Default the abort_conf malloc option to false.

This avoids troublesome backward compatibility issues.

Update jemalloc to 5.0.0.

Fix minor malloc regressions.

- Use _Bool rather than bool to resolve missing type errors in malloc_np.h.
- Fix malloc manual page #include documentation.
- Add *allocm manual pages to obsolete files.

Submitted by: jbeich

Add jemalloc support for 8 KiB, 16 KiB, and 64 KiB pages.

Update jemalloc to version 4.0.0.

Update jemalloc to version 3.5.0.

Update jemalloc to version 3.4.1.

Update list of ports required for importing jemalloc.

Import jemalloc 606f1fdc3cdbc700717133ca56685313caea24bb (dev branch,
prior to 3.0.0 release), and mangle internal symbols.

Import jemalloc 9ef7f5dc34ff02f50d401e41c8d9a4a928e7c2aa (dev branch,
prior to 3.0.0 release) as contrib/jemalloc, and integrate it into libc.
The code being imported by this commit diverged from
lib/libc/stdlib/malloc.c in March 2010, which means that a portion of
the jemalloc 1.0.0 ChangeLog entries are relevant, as are the entries
for all subsequent releases.