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