Let's recall what is really happening...
In maintainer mode, the build system sets -Werror and -Wstrict-prototypes.
This means that functions which lack strict prototypes will "fail".
Now note that AC_CHECK_LIB does not worry about generating
function calls w/ prototypes, so, for example, when checking
for luaL_newstate, it will fail *even if the function exists*!
In fact, this is how I 1st observed the issue: mod_lua was
no longer being included.
The long and short is that under maintainer mode, we cannot
expect AC_CHECK_LIB to being correct any longer, because
the combination of -Werror and -Wstrict-prototypes means
that any and all functions looked for/checked for using
AC_CHECK_LIB will NOT be found, due to warnings which are
now fatal errors during configure time, even if those
functions DO exist.
PS: CCing dev@apr since APR also uses AC_CHECK_LIB