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After fixing #13580 my build still fails with...

```
CXX compat/libbitcoin_util_a-glibc_sanity.o
In file included from compat/glibc_sanity.cpp:12:0:
compat/glibc_sanity.cpp: In function 'bool {anonymous}::sanity_test_fdelt()':
compat/glibc_sanity.cpp:53:5: error: 'memset' was not declared in this scope
FD_ZERO(&fds);
^
Makefile:6248: recipe for target 'compat/libbitcoin_util_a-glibc_sanity.o' failed
make[2]: *** [compat/libbitcoin_util_a-glibc_sanity.o] Error 1
make[2]: Leaving directory '/opt/local/src/bitcoin/src'
Makefile:9824: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/opt/local/src/bitcoin/src'
Makefile:757: recipe for target 'all-recursive' failed
make: *** [all-recursive] Error 1
```

I have attached 
[config.log](https://github.com/bitcoin/bitcoin/files/2152954/config.log) for your review.

#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif
#include <cstddef>
#if defined(HAVE_SYS_SELECT_H)
bool sanity_test_fdelt();
#endif
extern "C" void* memcpy(void* a, const void* b, size_t c);
void* memcpy_int(void* a, const void* b, size_t c)