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 5.0.1.

Update jemalloc to 5.0.0.

Update jemalloc to 4.5.0.

Update jemalloc to 4.4.0.

Update jemalloc to 4.3.1.

Update jemalloc to 4.2.1.

Update jemalloc to 4.2.0.

Restore support for decay time of -1 (no decay).

Add a cast to prevent a compiler warning.

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 4.0.4.

Update jemalloc to 4.0.2.

Update jemalloc to version 4.0.0.

Update jemalloc to version 3.6.0.

Update jemalloc to version 3.5.1.

Update jemalloc to version 3.5.0.

Update jemalloc to version 3.4.1.

Update jemalloc to version 3.4.0.

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

Import jemalloc 3.2.0.

Import jemalloc 3.0.0. This fixes memory zeroing bugs that manifested as
jemalloc assertion failures for debug builds, or as calloc() sometimes
returning non-zeroed memory for production builds.

Import jemalloc 37b6f95dcd866f51c91488531a2efc3ed4c2b754 (dev branch,
prior to 3.0.0 release). This version is likely very close to what will be
3.0.0.

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.