pgsql: Fix portability issues in pg_bitutils

Fix portability issues in pg_bitutils

We were using uint64 function arguments as "long int" arguments to
compiler builtins, which fails on machines where long ints are 32 bits:
the upper half of the uint64 was being ignored.  Fix by using the "ll"
builtin variants instead, which on those machines take 64 bit arguments.

Also, remove configure tests for __builtin_popcountl() (as well as
"long" variants for ctz and clz): the theory here is that any compiler
version will provide all widths or none, so one test suffices.  Were
this theory to be wrong, we'd have to add tests for
__builtin_popcountll() and friends, which would be tedious.

Per failures in buildfarm member lapwing and ensuing discussion.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/109de05cbb034b032cd60f50708716c8ff0afdf2

Modified Files
--------------
config/c-compiler.m4          |  58 ----------------
configure                     | 152 +++++++++++-------------------------------
configure.in                  |   7 +-
src/include/pg_config.h.in    |  21 ++----
src/include/pg_config.h.win32 |  21 ++----
src/port/pg_bitutils.c        |  73 ++++++++++----------
6 files changed, 87 insertions(+), 245 deletions(-)