Gaphics: Make frame skip a config option

When using something like Valgrind that will run
mkxp 20 times slower than normal, frame skip will
make the redraw loop completely grind to a halt.
Set 'frameSkip' to false in the config to
avert this.

src/config.cpp

@@ -38,6 +38,7 @@ Config::Config()
       defScreenW(640),
       defScreenH(480),
       fixedFramerate(0),
+      frameSkip(true),
       solidFonts(false),
       gameFolder("."),
       allowSymlinks(false)
@@ -58,6 +59,7 @@ void Config::read()
 	READ_VAL(defScreenW, Int);
 	READ_VAL(defScreenH, Int);
 	READ_VAL(fixedFramerate, Int);
+	READ_VAL(frameSkip, Bool);
 	READ_VAL(solidFonts,  Bool);
 	READ_VAL(gameFolder, ByteArray);
 	READ_VAL(allowSymlinks, Bool);

src/config.h

@@ -41,6 +41,7 @@ struct Config
 	int defScreenH;
 
 	int fixedFramerate;
+	bool frameSkip;
 
 	bool solidFonts;
 

src/graphics.cpp

@@ -583,12 +583,20 @@ void Graphics::update()
 
 	if (p->fpsLimiter.frameSkipRequired())
 	{
-		/* Skip frame */
-		p->fpsLimiter.delay();
-		++p->frameCount;
-		p->threadData->ethread->notifyFrame();
+		if (p->threadData->config.frameSkip)
+		{
+			/* Skip frame */
+			p->fpsLimiter.delay();
+			++p->frameCount;
+			p->threadData->ethread->notifyFrame();
 
-		return;
+			return;
+		}
+		else
+		{
+			/* Just reset frame adjust counter */
+			p->fpsLimiter.resetFrameAdjust();
+		}
 	}
 
 	p->checkResize();