* Makefile.am, configure.ac: Add new test for user configured stack
allocator/deallocator. Test both pass and fail cases.
* spstkalloc/.cvsignore, spstkalloc/Makefile.am, spstkalloc/init.c,
spstkalloc/spstkalloc.doc, spstkalloc/spstkalloc.scn: New files.
