sceImpose: Report HOME to POPS from sceImpose_9BA61B49

In impose.prx (6.60), it returns a flag impose's thread sets each pass while
HOME is held, but only if impose leaves HOME to the application. Its init
does that for application types 0x300 (POPS) and 0x400, and
sceImpose_9DBCE0C4 changes it. So games get 0, and the PS1 emulator, which
polls it to open its in-game menu, gets HOME.

It was unimplemented, so it returned SCE_KERNEL_ERROR_LIBRARY_NOT_YET_LINKED.

Core/HLE/sceImpose.cpp

@@ -20,6 +20,8 @@
 #include "Core/HLE/HLE.h"
 #include "Core/HLE/FunctionWrappers.h"
 #include "Core/HLE/ErrorCodes.h"
+#include "Core/HLE/PopsBoot.h"
+#include "Core/HLE/sceCtrl.h"
 #include "Core/HLE/sceImpose.h"
 #include "Core/HLE/sceUtility.h"
 #include "Core/MIPS/MIPS.h"
@@ -124,6 +126,14 @@ static u32 sceImposeGetBacklightOffTime() {
 	return hleLogDebug(Log::sceUtility, backlightOffTime);
 }
 
+// Whether HOME is held, when impose leaves HOME to the application. impose.prx's init does that
+// for POPS (and application type 0x400), so for a game it's always 0. The PS1 emulator polls it for
+// its menu.
+static u32 sceImpose_9BA61B49() {
+	const bool held = PopsBootActive() && (__CtrlPeekButtons() & CTRL_HOME) != 0;
+	return hleLogVerbose(Log::sceUtility, held ? 1 : 0);
+}
+
 // OSD stuff? home button?
 const HLEFunction sceImpose[] = {
 	{0X36AA6E91, &WrapU_UU<sceImposeSetLanguageMode>,      "sceImposeSetLanguageMode",      'i', "ii"},
@@ -139,7 +149,7 @@ const HLEFunction sceImpose[] = {
 	{0XFCD44963, nullptr,                                  "sceImpose_FCD44963",            '?', ""  },
 	{0XA9884B00, nullptr,                                  "sceImpose_A9884B00",            '?', ""  },
 	{0XBB3F5DEC, nullptr,                                  "sceImpose_BB3F5DEC",            '?', ""  },
-	{0X9BA61B49, nullptr,                                  "sceImpose_9BA61B49",            '?', ""  }, // jpcsp: isHomeButtonPressed() -> bool
+	{0X9BA61B49, &WrapU_V<sceImpose_9BA61B49>,             "sceImpose_9BA61B49",            'x', ""  },
 	{0XFF1A2F07, nullptr,                                  "sceImpose_FF1A2F07",            '?', ""  },
 };