SDL_endian.h: add Watcom inline asm for SDL_Swap16 and SDL_Swap32

include/SDL_endian.h

@@ -97,6 +97,12 @@ static __inline__ Uint16 SDL_Swap16(Uint16 x)
 	__asm__("rorw #8,%0" : "=d" (x) :  "0" (x) : "cc");
 	return x;
 }
+#elif defined(__WATCOMC__) && defined(__386__)
+extern _inline Uint16 SDL_Swap16(Uint16);
+#pragma aux SDL_Swap16 = \
+	"xchg al, ah" \
+	parm   [ax]   \
+	modify [ax];
 #else
 static __inline__ Uint16 SDL_Swap16(Uint16 x) {
 	return SDL_static_cast(Uint16, ((x<<8)|(x>>8)));
@@ -132,6 +138,21 @@ static __inline__ Uint32 SDL_Swap32(Uint32 x)
 	__asm__("rorw #8,%0\n\tswap %0\n\trorw #8,%0" : "=d" (x) :  "0" (x) : "cc");
 	return x;
 }
+#elif defined(__WATCOMC__) && defined(__386__)
+extern _inline Uint32 SDL_Swap32(Uint32);
+#ifndef __SW_3 /* 486+ */
+#pragma aux SDL_Swap32 = \
+	"bswap eax"  \
+	parm   [eax] \
+	modify [eax];
+#else  /* 386-only */
+#pragma aux SDL_Swap32 = \
+	"xchg al, ah"  \
+	"ror  eax, 16" \
+	"xchg al, ah"  \
+	parm   [eax]   \
+	modify [eax];
+#endif
 #else
 static __inline__ Uint32 SDL_Swap32(Uint32 x) {
 	return SDL_static_cast(Uint32, ((x<<24)|((x<<8)&0x00FF0000)|((x>>8)&0x0000FF00)|(x>>24)));