Add test/jemalloc_test.h.in, which is processed to include
jemalloc/jemalloc@install_suffix@.h, so that test programs can include
it without worrying about the install suffix.
Add allocm(), rallocm(), sallocm(), and dallocm(), which are a
functional superset of malloc(), calloc(), posix_memalign(),
malloc_usable_size(), and free().
