string: add and test strpbrk (DONE)

CMakeLists.txt

@@ -150,6 +150,7 @@ set(SOURCES
   src/libc/string/strncpy.c
   src/libc/string/strndup.c
   src/libc/string/strnlen.c
+  src/libc/string/strpbrk.c
   src/libc/string/strrchr.c
   src/libc/string/strspn.c
   src/libc/string/strxfrm.c)

STATUS

@@ -123,7 +123,7 @@ DONE:       Function/symbol/macro is defined, builds, links, and is tested
      7.21.5.1  memchr: DONE
      7.21.5.2  strchr: DONE
      7.21.5.3  strcspn: DONE
-!    7.21.5.4  strpbrk: TODO
+     7.21.5.4  strpbrk: DONE
      7.21.5.5  strrchr: DONE
      7.21.5.6  strspn: DONE
 !    7.21.5.7  strstr: TODO

src/libc/string/strpbrk.c

@@ -0,0 +1,10 @@
+#include <string.h>
+
+char *strpbrk(char const *str, char const *accept)
+{
+	for(size_t i = 0; str[i]; i++) {
+		if(strchr(accept, str[i])) return (char *)&str[i];
+	}
+
+	return NULL;
+}