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>

makeflags

@@ -10,4 +10,4 @@ CCFLAGS = -Wall -Wextra -Werror -O3
 CCFLAGS += -I../include -D_FILE_OFFSET_BITS=64
 
 BEES_CFLAGS   = $(CCFLAGS) -std=c99 $(CFLAGS)
-BEES_CXXFLAGS = $(CCFLAGS) -std=c++11 -Wold-style-cast $(CXXFLAGS)
+BEES_CXXFLAGS = $(CCFLAGS) -std=c++11 -Wold-style-cast -Wno-missing-field-initializers $(CXXFLAGS)