* configure.ac (--enable-m-guard): Remove.
* src/global.c (_gcry_vcontrol): Return GPG_ERR_NOT_SUPPORTED for
GCRYCTL_ENABLE_M_GUARD.
* src/stdmem.c (use_m_guard, _gcry_private_enable_m_guard): Remove.
(_gcry_private_malloc): Remove the code path with use_m_guard==1.
(_gcry_private_malloc_secure): Likewise.
(_gcry_private_realloc, _gcry_private_free): Likewise.
(_gcry_private_check_heap): Remove.
* src/stdmem.h: Remove declarations for memory guard functions.