Revert "regressions: Benchmark coverage for latchlock operations."

This reverts commit 24d65432e0514044965e066d426a5cac3d603972.
ck_rwlock: Ditch ck_rwlock latch for ck_swlock.
Revert "ck_rwlock: Additional reorganization."

This reverts commit 56de32fffde906357ed0bb5e42555c84b522a08a.
Revert "ck_rwlock: Additional re-organization of write-side functions."

This reverts commit d9b86d2d89883a07317980eb37b2216b62291d52.
Revert "ck_rwlock: Re-organization of write-side operations and latch support for write_trylock."

This reverts commit ab22fda4e75853c18653956cf0de172a6aa5cd39.
Revert "ck_rwlock: Ignore latch bits on write lock operation."

This reverts commit 8173b937bf71bb7fd4824ece0181d8419235c788.
Revert "ck_rwlock: Add ck_rwlock_read_latchlock operation."

This reverts commit bc7ebc62eb69f3418cf51573fb13dea85369f5a3.
Revert "ck_rwlock: Acquire semantics for ordering on  latch bits."

This reverts commit 2b567320de8c1b67c386a8b42165ca124a7bcca8.
Revert "ck_rwlock: Re-observe latch bits if necessary."

This reverts commit fa286223861165ee5617712a9bf9c6e6553be3fd.
Revert "ck_rwlock: Clear reader bits on unlatch operation."

This reverts commit 7f945460bccec3ab64eeecf18841c2cc33e0c8f9.
Revert "ck_rwlock: Use sub for unlatch operation."

This reverts commit b7c3c8a43d95e38d4bb942d9113aa9c9e24f0f23.
Revert "ck_rwlock: Migrate to 32-bit primitives and add a write_latch operation."

This reverts commit 210b724061bda62065070cc156300ae49a4c6194.

Conflicts:
	include/ck_rwlock.h
ck_rwlock: Fix conflict.

ck_swlock will be a copy-safe single-writer multi-reader lock that
will meet our requirements.
regressions: Remove latchlock coverage.
ck_cc: new bitwise ops

GCC and compatible compilers support ffs/ctz/clz/popcount. Expose that
in ck_cc and default to slow but portable software emulation.
ck_bitmap: more bulk operations, less space, more tests

* new bulk rmw: intersection, intersection_negate (with complement),
* new bulk reads: empty, full, count, count_intersect

* ck_bitmap_iterator fixes: avoid out of bounds read on empty bitmaps,
  and ck_bitmap_next is marginally faster on sparse bitmaps .

* less space: the bitmap itself is an array of unsigned int, which
  eliminates alignment padding between the n_bit field and the bitmap.

* more unit tests.
gitignore: add regressions/ck_spinlock/validate/ck_hclh

 and sort regressions/ noise alphabetically.