remove or make static various unused __-prefixed symbols

src/string/strdup.c

@@ -1,13 +1,10 @@
 #include <stdlib.h>
 #include <string.h>
-#include "libc.h"
 
-char *__strdup(const char *s)
+char *strdup(const char *s)
 {
 	size_t l = strlen(s);
 	char *d = malloc(l+1);
 	if (!d) return NULL;
 	return memcpy(d, s, l+1);
 }
-
-weak_alias(__strdup, strdup);