Fixes for more discerning compilers.

benchmarks/main.c

@@ -24,7 +24,10 @@ int main (int argc, char *argv[])
   char *progname = argv[0];
   if(lastslash) {
     *lastslash = '\0';
-    chdir(argv[0]);
+    if(chdir(argv[0]) < 0) {
+      fprintf(stderr, "Error changing directory to %s.\n", argv[0]);
+      return 1;
+    }
     *lastslash = '/';
     progname = lastslash + 3;  /* "/b_" */
   }

src/upb_string.h

@@ -96,7 +96,7 @@ INLINE struct upb_string *upb_strdup(struct upb_string *s) {
   return copy;
 }
 
-INLINE struct upb_string *upb_strdupc(char *s) {
+INLINE struct upb_string *upb_strdupc(const char *s) {
   struct upb_string *copy = upb_string_new();
   copy->byte_len = strlen(s);
   upb_string_resize(copy, copy->byte_len);