Add fixed-point math parity test

Makes sure the more complex functions match regardless of bitdepth
Currently (and very likely to stay) only FixedSqrt

src/console.c

@@ -1654,6 +1654,7 @@ static const char *CON_LoadingStrings[LOADED_ALLDONE+1] =
 	"Init rendering daemon...", //LOADED_RINIT
 	"Init audio subsystem...", //LOADED_SINITSFXCHANNELS
 	"Cache HUD...", //LOADED_STINIT
+	"Test fixed-point arithmetic...", //LOADED_MATHINIT
 	"Init ACSVM...", //LOADED_ACSINIT
 	"Check game status...", //LOADED_DCHECKNETGAME
 	"Now starting..."

src/console.h

@@ -52,6 +52,7 @@ typedef enum
 	LOADED_RINIT,
 	LOADED_SINITSFXCHANNELS,
 	LOADED_STINIT,
+	LOADED_MATHINIT,
 	LOADED_ACSINIT,
 	LOADED_DCHECKNETGAME,
 	LOADED_ALLDONE = LOADED_DCHECKNETGAME,

src/d_main.cpp

@@ -1814,6 +1814,61 @@ void D_SRB2Main(void)
 	ST_Init();
 	CON_SetLoadingProgress(LOADED_STINIT);
 
+	CONS_Printf("FixedSqrt of 32767 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(0x7FFF0000),
+				FixedSqrt64(0x7FFF0000));
+
+	if (FixedSqrt(0x7FFF0000) == FixedSqrt64(0x7FFF0000))
+	{
+		CONS_Printf("\x83" "32767: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "32767: Test NG!" "\x80" "\n");
+	}
+
+	CONS_Printf("FixedSqrt of 4 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(0x40000),
+				FixedSqrt64(0x40000));
+
+	if (FixedSqrt(0x40000) == FixedSqrt64(0x40000))
+	{
+		CONS_Printf("\x83" "4: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "4: Test NG!" "\x80" "\n");
+	}
+
+	// You should probably generate the weird number with RANDOM.org
+#define WEIRDNUMBER 3886284 /* 59.3 fracunits; this should approximate to around 7 */
+	CONS_Printf("FixedSqrt of 59.3 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(WEIRDNUMBER),
+				FixedSqrt64(WEIRDNUMBER));
+
+	if (FixedSqrt(WEIRDNUMBER) == FixedSqrt64(WEIRDNUMBER))
+	{
+		CONS_Printf("\x83" "59.3: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "59.3: Test NG!" "\x80" "\n");
+	}
+#undef WEIRDNUMBER
+
+	CONS_Printf("FixedSqrt64 of 65535 fracunits: %d (not possible at 32-bit scale)\n",
+				FixedSqrt64(0xFFFFFFFF));
+
+	CONS_Printf("IntSqrt of 32767: %d; IntSqrt64: %d\n",
+				IntSqrt(0x7FFF),
+				IntSqrt64(0x7FFF));
+
+	CONS_Printf("IntSqrt of 4: %d; IntSqrt64: %d\n",
+				IntSqrt(4),
+				IntSqrt64(4));
+
+	CON_SetLoadingProgress(LOADED_MATHINIT);
+
 	CONS_Printf("ACS_Init(): Init Action Code Script VM.\n");
 	ACS_Init();
 	CON_SetLoadingProgress(LOADED_ACSINIT);