fix standalone warnings

armsrc/string.h

@@ -33,6 +33,8 @@ char *strrchr(const char *s, int c);
 size_t strcspn(const char *s1, const char *s2);
 char *strpbrk(const char *s1, const char *s2);
 int strncmp(const char *s1, const char *s2, size_t n);
+unsigned long strtoul(const char *p, char **out_p, int base);
+long strtol(const char *p, char **out_p, int base);
 char c_tolower(int c);
 char c_isprint(unsigned char c);