Enable -Wextra in tests.

tests/stdlib/alloc.c

@@ -89,7 +89,7 @@ int main(void) {
     size_t nonpow2_mul_voidptr_size = 3*sizeof(void *);
     size_t pow2_mul_voidptr_size = 4*sizeof(void *);
     
-    int i;
+    size_t i;
     
     errno = 0;
     char * ptr_zerosize_malloc = (char *)malloc(zero_size);

tests/stdlib/qsort.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <stddef.h>
 #include <stdlib.h>
 
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
@@ -12,7 +13,7 @@ int cmpfunc (const void * a_ptr, const void * b_ptr) {
 }
 
 int main () {
-    int i;
+    size_t i;
 
     printf("Before: ");
     for(i = 0; i < ARRAY_SIZE(values); i++) {

tests/stdlib/strtod.c

@@ -1,3 +1,4 @@
+#include <stddef.h>
 #include <stdlib.h>
 #include <stdio.h>
 
@@ -73,7 +74,7 @@ int main(void) {
         "-NaN0.1e5", "-nan-37", "-nAn1.05", "-Nan foo bar baz",
 
     };
-    for (int i = 0; i < sizeof(inputs) / sizeof(char*); i += 1) {
+    for (size_t i = 0; i < sizeof(inputs) / sizeof(char*); i += 1) {
         d = strtod(inputs[i], &endptr);
         printf("d: %f Endptr: \"%s\"\n", d, endptr);
     }