secp256k1-sys 0.13.0

FFI for Pieter Wuille's `libsecp256k1` library.
Documentation
14d13
< #include <stdio.h>
22,41d20
< /* Debug helper for printing arrays of unsigned char. */
< #define PRINT_BUF(buf, len) do { \
<     printf("%s[%lu] = ", #buf, (unsigned long)len); \
<     print_buf_plain(buf, len); \
< } while(0)
< 
< static void print_buf_plain(const unsigned char *buf, size_t len) {
<     size_t i;
<     printf("{");
<     for (i = 0; i < len; i++) {
<         if (i % 8 == 0) {
<             printf("\n    ");
<         } else {
<             printf(" ");
<         }
<         printf("0x%02X,", buf[i]);
<     }
<     printf("\n}\n");
< }
< 
148,152c127,129
<     void *ret = malloc(size);
<     if (ret == NULL) {
<         secp256k1_callback_call(cb, "Out of memory");
<     }
<     return ret;
---
>     (void) cb;
>     (void) size;
>     return NULL;