pgsql: Use "grep -E" not "egrep".

Use "grep -E" not "egrep".

"egrep" has never been in POSIX; the standard way to access this
functionality is "grep -E". Recent versions of GNU grep have
started to warn about this, so stop using "egrep".

This could be back-patched, but I see little need to do so
because the affected places are not code that runs during
normal builds. (Perhaps src/backend/port/aix/mkldexport.sh
is an exception, but let's wait to see if any AIX users
complain before touching that.)

Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Discussion: https://postgr.es/m/473272.1778685870@sss.pgh.pa.us

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/2122281672b4505c6fa391899d8af2318770a102

Modified Files
--------------
doc/src/sgml/func/func-matching.sgml | 4 ++--
src/backend/port/aix/mkldexport.sh | 4 ++--
src/tools/find_typedef | 6 +++---
src/tools/perlcheck/find_perl_files | 2 +-
4 files changed, 8 insertions(+), 8 deletions(-)