keep -DAP_HOOK_PROBES_ENABLED (--enable-hook-probes) and

-DAP_DECLARE_EXPORT (MinGW builds) out of the *CPPFLAGS
used for third-party module builds

introduce INTERNAL_CPPFLAGS for that; apxs bypasses this


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1101211 13f79535-47bb-0310-9956-ffa450edef68