Remove flawed alignment-related overflow test.

Remove the allocm() test equivalent to the mallocx() test removed in the
previous commit.  The flawed test attempted to cause OOM due to large
request size and alignment constraint.  Although this test "passed" on
64-bit systems due to the virtual memory hole, it could pass on some
32-bit systems.
Prevent inlining of backtraced test functions.

Inlining of alloc_0() and alloc_1() would prevent generation of unique
backtraces, upon which the test code relies.