Fix the latent tail from the Common/Core review

Buffer::PeekAll resized the destination and then appended, so it returned twice the
data with zeros in front. No callers today.

The assert dialog's caption was a function-local static, so it froze at whichever
kind of assert fired first in the session - a later Critical Assert would still be
titled 'Debug Assert'. Made it a plain const char *.

containsNoCase passed a possibly-negative char to std::toupper, which is UB for
anything but EOF; non-ASCII bytes get here from ELF symbol names.

ApplyDeadzoneXY's circular path lacked the deadzone >= 0.99f guard its own sibling
ApplyDeadzoneAxis has one function above, so it divided by ~0.

Core/TiltEventProcessor.cpp

@@ -55,6 +55,13 @@ inline float ApplyDeadzoneAxis(float x, float deadzone) {
 
 inline void ApplyDeadzoneXY(float x, float y, float *adjustedX, float *adjustedY, float deadzone, bool circular) {
 	if (circular) {
+		if (deadzone >= 0.99f) {
+			// Same guard as ApplyDeadzoneAxis - without it the factor below divides by ~0.
+			*adjustedX = x;
+			*adjustedY = y;
+			return;
+		}
+
 		if (x == 0.0f && y == 0.0f) {
 			*adjustedX = 0.0f;
 			*adjustedY = 0.0f;