pgsql: Rely on __func__ being supported

Rely on __func__ being supported

Previously we fell back to __FUNCTION__ and then NULL. As __func__ is in C99
that shouldn't be necessary anymore.

Solution.pm defined HAVE_FUNCNAME__FUNCTION instead of
HAVE_FUNCNAME__FUNC (originating in 4164e6636e2), as at some point in the past
MSVC only supported __FUNCTION__. Our minimum version supports __func__.

Reviewed-By: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/20220807012914.ydz73yte6j3coulo@awork3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/320f92b744b44f961e5d56f5f21de003e8027a7f

Modified Files
--------------
config/c-compiler.m4              | 26 -----------------
configure                         | 61 ---------------------------------------
configure.ac                      |  1 -
src/backend/storage/lmgr/s_lock.c |  2 +-
src/include/c.h                   | 11 -------
src/include/pg_config.h.in        |  6 ----
src/include/storage/s_lock.h      |  4 +--
src/include/utils/elog.h          |  4 +--
src/tools/msvc/Solution.pm        |  2 --
9 files changed, 5 insertions(+), 112 deletions(-)