engine: fix UB on MSG_BigShort

engine/common/net_buffer.c

@@ -27,7 +27,7 @@ GNU General Public License for more details.
 static dword	BitWriteMasks[32][33];
 static dword	ExtraMasks[32];
 
-short MSG_BigShort( short swap )
+unsigned short MSG_BigShort( unsigned short swap )
 {
 	return (swap >> 8)|(swap << 8);
 }

engine/common/net_buffer.h

@@ -63,7 +63,7 @@ void MSG_ExciseBits( sizebuf_t *sb, int startbit, int bitstoremove );
 _inline int MSG_TellBit( sizebuf_t *sb ) { return sb->iCurBit; }
 _inline const char *MSG_GetName( sizebuf_t *sb ) { return sb->pDebugName; }
 qboolean MSG_CheckOverflow( sizebuf_t *sb );
-short MSG_BigShort( short swap );
+unsigned short MSG_BigShort( unsigned short swap );
 
 // init writing
 void MSG_StartWriting( sizebuf_t *sb, void *pData, int nBytes, int iStartBit, int nBits );