Replace zlib, zstd, libchdr, libzip and libpng with libretro-common

Deflate, zlib and gzip streams go through rinflate and rdeflate, zstd
through rzstd, CHD images through rchd, zip archives through
rzip_archive and PNG through rpng. The bundled libraries, their build
glue and the system-library options are gone; adler32 and uncompress
keep zlib's ABI for the prebuilt FFmpeg archives that still call them.
libretro-common is one CMake library that the core, the headless tool
and the unit tests all link.

The reads take shorter paths on the way. CHD decodes straight from the
loader's reads and a range of blocks at a time, and a file read at any
alignment decodes into place; CSO keeps one inflate stream instead of
one per block; a plain ISO serves a file read with one read of its exact
bytes; a stored zip member is read in place and a deflated one through
restart points rather than a copy of the whole image in memory; zip
members decode into the caller's buffer; sequential reads through the
frontend's VFS skip the seek, which also keeps its buffering.

libretro/test reads one image as ISO, CSO, CHD and zip through the block
devices, boots each, and checks the codecs against Python-made vectors;
a CI job runs it.

Core/Loaders.cpp

@@ -388,7 +388,7 @@ bool UmdReplace(const Path &filepath, FileLoader **fileLoader, std::string &erro
 // Close the return value with ZipClose (if non-null, of course).
 ZipContainer ZipOpenPath(const Path &fileName) {
 	ZipContainer z(fileName);
-	if (z == nullptr) {
+	if (!z) {
 		ERROR_LOG(Log::HLE, "Failed to open ZIP file '%s'", fileName.c_str());
 	}
 	return z;
@@ -438,43 +438,23 @@ inline char asciitolower(char in) {
 // i.e. straight from an untrusted file.
 static const u64 MAX_ZIP_EXTRACT_TO_MEMORY_SIZE = 16 * 1024 * 1024;
 
-static bool ZipExtractFileToMemory(struct zip *z, int fileIndex, std::string *data) {
-	zip_stat_t zstat{};
-	if (zip_stat_index(z, fileIndex, 0, &zstat) != 0) {
-		ERROR_LOG(Log::HLE, "zip_stat_index failed for file %d in zip", fileIndex);
-		return false;
-	}
-	if (!(zstat.valid & ZIP_STAT_SIZE)) {
-		ERROR_LOG(Log::HLE, "No size for file %d in zip", fileIndex);
-		return false;
-	}
-	if (zstat.size == 0) {
+static bool ZipExtractFileToMemory(const ZipContainer &z, int fileIndex, std::string *data) {
+	const u64 size = z.Size(fileIndex);
+	if (size == 0) {
 		data->clear();
 		return true;
 	}
-	if (zstat.size > MAX_ZIP_EXTRACT_TO_MEMORY_SIZE) {
-		ERROR_LOG(Log::HLE, "Refusing to extract file %d from zip: declared size %llu is implausible", fileIndex, (unsigned long long)zstat.size);
+	if (size > MAX_ZIP_EXTRACT_TO_MEMORY_SIZE) {
+		ERROR_LOG(Log::HLE, "Refusing to extract file %d from zip: declared size %llu is implausible", fileIndex, (unsigned long long)size);
 		return false;
 	}
-
-	size_t readSize = (size_t)zstat.size;
-	data->resize(readSize);
-
-	zip_file *zf = zip_fopen_index(z, fileIndex, 0);
-	if (!zf) {
-		ERROR_LOG(Log::HLE, "Failed to zip_fopen_index file %d from zip", fileIndex);
+	data->resize((size_t)size);
+	if (!z.ExtractInto(fileIndex, (uint8_t *)&(*data)[0], data->size())) {
+		ERROR_LOG(Log::HLE, "Failed to read %d bytes from zip - archive corrupt?", (int)size);
+		data->clear();
 		return false;
 	}
-
-	zip_int64_t retval = zip_fread(zf, data->data(), readSize);
-	zip_fclose(zf);
-
-	if (retval < 0 || retval < (int)readSize) {
-		ERROR_LOG(Log::HLE, "Failed to read %d bytes from zip (%d) - archive corrupt?", (int)readSize, (int)retval);
-		return false;
-	} else {
-		return true;
-	}
+	return true;
 }
 
 // TODO: Make this generic and handle all the things.
@@ -495,16 +475,15 @@ bool DetectArchiveContents(VFSInterface *vfs, ZipFileInfo *info) {
 	return false;
 }
 
-void DetectZipFileContents(zip_t *z, ZipFileInfo *info) {
+void DetectZipFileContents(const ZipContainer &z, ZipFileInfo *info) {
 	info->archiveType = ArchiveType::ZIP;
-	int numFiles = zip_get_num_files(z);
-	if (numFiles < 0) {
+	if (!z) {
 		// Broken zip archive?
 		ERROR_LOG(Log::HLE, "Failed to get the file count of zip file");
 		info->contents = ZipFileContents::UNKNOWN;
 		return;
 	}
-	_dbg_assert_(numFiles >= 0);
+	const int numFiles = z.NumEntries();
 
 	// Verify that this is a PSP zip file with the correct layout. We also try
 	// to detect simple zipped ISO files, those we'll just "install" to the current
@@ -528,11 +507,10 @@ void DetectZipFileContents(zip_t *z, ZipFileInfo *info) {
 	// TODO: It might be cleaner to write separate detection functions, but this big loop doing it all at once
 	// is quite convenient and makes it easy to add shared heuristics.
 	for (int i = 0; i < numFiles; i++) {
-		const char *fn = zip_get_name(z, i, 0);
-
-		zip_stat_t stat{};
-		zip_stat_index(z, i, 0, &stat);
-		totalFileSize += stat.size;
+		const char *fn = z.Name(i);
+		if (!fn)
+			continue;
+		totalFileSize += z.Size(i);
 
 		std::string fileName(fn);
 		if (endsWith(fileName, "/")) {
@@ -599,9 +577,6 @@ void DetectZipFileContents(zip_t *z, ZipFileInfo *info) {
 					if (sfo.HasKey("TITLE")) {
 						info->gameTitle = sfo.GetValueString("TITLE");
 						info->savedataTitle = sfo.GetValueString("SAVEDATA_TITLE");
-						char buff[20];
-						strftime(buff, 20, "%Y-%m-%d %H:%M:%S", localtime(&stat.mtime));
-						info->mTime = buff;
 						info->savedataDetails = sfo.GetValueString("SAVEDATA_DETAIL");
 						info->savedataDir = sfo.GetValueString("SAVEDATA_DIRECTORY");  // should also be parsable from the path.
 						hasParamSFO = true;