Trouble building with external pal

[opoplawski]

I'm working on changing the Fedora ast package to build with an external pal lib. However, I'm running into a couple issues:

• Fedora does not ship .la files, but ast is trying to link to $(libdir)/libpal.la. I've changed this to -lpal.
• ast_test does not appear to consider the conditional and still references @LIBPAL@, @LIBCMINPACK@, libast_pal.la and libast_cminpack.la in LDADD and DEPENDENCIES