eval: Fix 32bit unsigned parsing

Fixes ticket264
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavutil/eval.c

@@ -76,7 +76,7 @@ double av_strtod(const char *numstr, char **tail)
     double d;
     char *next;
     if(numstr[0]=='0' && (numstr[1]|0x20)=='x') {
-        d = strtol(numstr, &next, 16);
+        d = strtoul(numstr, &next, 16);
     } else
         d = strtod(numstr, &next);
     /* if parsing succeeded, check for and interpret postfixes */