some potential fixes for srcdir, need someone with deps to tell me what doesn't actually work here now

Mike removed mod_voipcodecs from tree in commit
bcd9f49f.

We'd long since replaced mod_voipcodecs with mod_spandsp.

Things seem to go wrong when building mod_ldap with make -j.

This allows building mod_soundtouch in clang as clang doesn't support
gcc's -fcheck-new.

FS-6293: fix lua to build using automake, so it works right with srcdir, and avoids the linking to .a is not portable warning

build spandsp core elements as a conv lib so we can use didfferent cflags to include the right config.h when building those files

FS-6293: abandon xmlrpc-c build system entirely.  We can revist this when we try to pull this lib out of tree, in the mean time, this fixes a ton of problems.