Update jemalloc to version 5.2.1

Revert r354606 to restore r354605.

Apply one line from jemalloc commit d01b425e5d1e1 in hash_x86_128()
to fix the build with gcc, which only allows a fallthrough attribute
to appear before a case or default label.

Submitted by: jasone in r354605
Discussed with: jasone
Reviewed by: bdrewery
MFC after: never, due to gcc 4.2.1
Relnotes: yes
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D24522

Revert r354605: Update jemalloc to version 5.2.1.

Compilation fails for non-llvm-based platforms.

Update jemalloc to version 5.2.1.

Update jemalloc to version 5.1.0.

Update jemalloc to 5.0.0.

Update jemalloc to 4.1.0.

Add missing Symbol.map entry for __aligned_alloc.

Add weak-->strong symbol binding for
{malloc_stats_print,mallctl,mallctlnametomib,mallctlbymib} -->
{__malloc_stats_print,__mallctl,__mallctlnametomib,__mallctlbymib}. These
bindings complete the set necessary to allow applications to replace all
malloc-related symbols.

Update jemalloc to version 4.0.0.

Update jemalloc to version 3.5.0.

Import jemalloc 3.3.0. This reduces zeroed memory validation overhead for
non-MALLOC_PRODUCTION builds.

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.