lib: deprecate memset_zero template, use C99 compound literals instead

Sprinkle in some asserts to make sure compilers aren't getting creative.

This may introduce a new compiler dependency, as I suspect older versions
of GCC don't support this syntax.

It definitely needs a new compiler flag to suppress a warning when some
fields are not explicitly initialized.  If we've omitted a field, it's
because it's a field we don't know (or care) about, and we want that
thing initialized to zero.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>

include/crucible/string.h

@@ -11,14 +11,6 @@
 namespace crucible {
 	using namespace std;
 
-	// Zero-initialize a base class object (usually a C struct)
-	template <class Base>
-	void
-	memset_zero(Base *that)
-	{
-		memset(that, 0, sizeof(Base));
-	}
-
 	// int->hex conversion with sprintf
 	string to_hex(uint64_t i);