Retire src/backend/utils/misc/check_guc

This script has existed for a long time, and attempting to run it today
causes a lot of false positives as an effect of GUCs added in the last
couple of years.  An equivalent, automatically-run and cross-platform
solution is available in the TAP test introduced in b0a55f4.  So, let it
go.

Discussion: https://postgr.es/m/Yf9YGSwPiMu0c7fP@paquier.xyz

src/backend/utils/misc/check_guc

@@ -1,78 +0,0 @@
-#!/bin/sh
-
-## currently, this script makes a lot of assumptions:
-## in postgresql.conf.sample:
-##   1) the valid config settings may be preceded by a '#', but NOT '# '
-##      (we use this to skip comments)
-##   2) the valid config settings will be followed immediately by  ' ='
-##      (at least one space preceding the '=')
-## in guc.c:
-##   3) the options have PGC_ on the same line as the option
-##   4) the options have '{' on the same line as the option
-
-##  Problems
-## 1) Don't know what to do with TRANSACTION ISOLATION LEVEL
-
-## if an option is valid but shows up in only one file (guc.c but not
-## postgresql.conf.sample), it should be listed here so that it
-## can be ignored
-INTENTIONALLY_NOT_INCLUDED="debug_deadlocks in_hot_standby \
-is_superuser lc_collate lc_ctype lc_messages lc_monetary lc_numeric lc_time \
-pre_auth_delay role seed server_encoding server_version server_version_num \
-session_authorization trace_lock_oidmin trace_lock_table trace_locks trace_lwlocks \
-trace_notify trace_userlocks transaction_isolation transaction_read_only \
-zero_damaged_pages"
-
-### What options are listed in postgresql.conf.sample, but don't appear
-### in guc.c?
-
-# grab everything that looks like a setting and convert it to lower case
-SETTINGS=`grep ' =' postgresql.conf.sample |
-grep -v '^# ' | # strip comments
-sed -e 's/^#//' |
-awk '{print $1}'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
-for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  ## it doesn't seem to make sense to have things in .sample and not in guc.c
-#  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-#    if [ "$hidethis" = "$i" ] ; then
-#      hidden=1
-#    fi
-#  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '"'$i'"' guc.c > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from guc.c";
-    fi;
-  fi
-done
-
-### What options are listed in guc.c, but don't appear
-### in postgresql.conf.sample?
-
-# grab everything that looks like a setting and convert it to lower case
-
-SETTINGS=`grep '{.* PGC_' guc.c | awk '{print $1}' | \
-          sed -e 's/{//g' -e 's/"//g' -e 's/,//'`
-
-SETTINGS=`echo "$SETTINGS" | tr 'A-Z' 'a-z'`
-
-for i in $SETTINGS ; do
-  hidden=0
-  ## it sure would be nice to replace this with an sql "not in" statement
-  for hidethis in $INTENTIONALLY_NOT_INCLUDED ; do
-    if [ "$hidethis" = "$i" ] ; then
-      hidden=1
-    fi
-  done
-  if [ "$hidden" -eq 0 ] ; then
-    grep -i '#'$i' ' postgresql.conf.sample > /dev/null
-    if [ $? -ne 0 ] ; then
-      echo "$i seems to be missing from postgresql.conf.sample";
-    fi
-  fi
-done