Add strrchr()

diff -r f2711b7eae95 -r 36bf1e737b87 extras/mini-os/include/lib.h
@@ -87,6 +87,7 @@
 size_t strnlen(const char *s, size_t count);
 size_t strlen(const char *s);
 char  *strchr(const char *s, int c);
+char  *strrchr(const char *s, int c);
 char  *strstr(const char *s1, const char *s2);
 char * strcat(char * dest, const char * src);
 char  *strdup(const char *s);

@@ -140,6 +140,15 @@
         return (char *)s;
 }
 
+char * strrchr(const char * s, int c)
+{
+        const char *res;
+        for(; *s != '\0'; ++s)
+                if (*s == (char) c)
+                        res = s;
+        return (char *)res;
+}
+
 char * strstr(const char * s1,const char * s2)
 {
         int l1, l2;