public: replace our Q_strlen with standard strlen with nullptr check in macro

public/crtlib.c

@@ -60,23 +60,6 @@ qboolean Q_isdigit( const char *str )
 	return false;
 }
 
-size_t Q_strlen( const char *string )
-{
-	size_t		len;
-	const char	*p;
-
-	if( !string ) return 0;
-
-	len = 0;
-	p = string;
-	while( *p )
-	{
-		p++;
-		len++;
-	}
-	return len;
-}
-
 size_t Q_colorstr( const char *string )
 {
 	size_t		len;

public/crtlib.h

@@ -50,7 +50,7 @@ enum
 void Q_strnupr( const char *in, char *out, size_t size_out );
 #define Q_strlwr( in, out ) Q_strnlwr( in, out, 99999 )
 void Q_strnlwr( const char *in, char *out, size_t size_out );
-size_t Q_strlen( const char *string );
+#define Q_strlen( str ) (( str ) ? strlen(( str )) : 0 )
 size_t Q_colorstr( const char *string );
 char Q_toupper( const char in );
 char Q_tolower( const char in );