pgsql: Remove fls(), use pg_leftmost_one_pos32() instead.

Remove fls(), use pg_leftmost_one_pos32() instead.

Commit 4f658dc8 provided the traditional BSD fls() function in
src/port/fls.c so it could be used in several places. Later we added a
bunch of similar facilities in pg_bitutils.h, based on compiler
builtins that map to hardware instructions. It's a bit confusing to
have both 1-based and 0-based variants of this operation in use in
different parts of the tree, and neither is blessed by a standard.
Let's drop fls.c and the configure probe, and reuse the newer code.

Reviewed-by: David Rowley <dgrowleyml(at)gmail(dot)com>
Reviewed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Discussion: https://postgr.es/m/CA%2BhUKG%2B7dSX1XF8yFGmYk-%3D48dbjH2kmzZj16XvhbrWP-9BzRg%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4f1f5a7f85cee932c417aef589b27574813a06c9

Modified Files
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configure | 13 -------
configure.ac | 1 -
src/backend/access/hash/hashutil.c | 2 +-
src/backend/optimizer/path/allpaths.c | 5 +--
src/backend/optimizer/prep/prepunion.c | 2 +-
src/backend/utils/mmgr/dsa.c | 14 +++++++-
src/include/pg_config.h.in | 3 --
src/include/port.h | 4 ---
src/port/fls.c | 64 ----------------------------------
src/tools/msvc/Mkvcbuild.pm | 2 +-
src/tools/msvc/Solution.pm | 1 -
11 files changed, 19 insertions(+), 92 deletions(-)