Subject: use bzero() instead of memset_s()

lib/replace/replace.h header defines ZERO_STRUCT macro
which uses memset_s() function (which is similar to
memset() but can not be optimized out by the compiler).
Glibc has bzero() with similar property, while memset_s()
have is implemented in lib/replace/replace.c, - this way,
some binaries needlessly link with libreplace-samba4 just
to get rep_memset_s() symbol. By using bzero() instead,
this endless linkage is eliminated, so we can package,
for example, libldb (which uses ZERO_STRUCT) without it
linking to libreplace-samba4.

Note: actually using explicit_bzero() so it is not optimized
out by the compiler - this is the original goal of using
memset_s().

diff --git a/lib/replace/replace.h b/lib/replace/replace.h
index 8609d84322c..28db8d425a3 100644
--- a/lib/replace/replace.h
+++ b/lib/replace/replace.h
@@ -822 +822 @@
-#define ZERO_STRUCT(x) memset_s((char *)&(x), sizeof(x), 0, sizeof(x))
+#define ZERO_STRUCT(x) explicit_bzero((char *)&(x), sizeof(x))