configury: add lua header fallback when cross compiling.
configury: add lua header fallback when cross compiling.

* m4/ax_lua.m4 (AX_LUA_HEADERS): Assume header version has been
set up correctly when cross-compiling.
From Christian Ege.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/slingshot