Merge branch 'calloc_overflow_check' into 'master'

add calloc integer overflow check

See merge request redox-os/relibc!188

tests/stdlib/alloc.c

@@ -1,6 +1,7 @@
 #include <malloc.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h> /* for SIZE_MAX */
 
 int main(void) {
     char * ptr = (char *)malloc(256);
@@ -18,6 +19,10 @@ int main(void) {
     }
     free(ptrc);
 
+    char * ptrco = (char *)calloc(SIZE_MAX, SIZE_MAX);
+    printf("calloc (overflowing) %p\n", ptrco);
+    free(ptrco); /* clean up correctly even if overflow is not handled */
+
     char * ptra = (char *)memalign(256, 256);
     printf("memalign %p\n", ptra);
     for(i = 0; i < 256; i++) {