pgsql: Remove --verbose from PROVE_FLAGS

Remove --verbose from PROVE_FLAGS

Per discussion, the TAP tests are really more verbose than necessary, so
remove the --verbose flag from PROVE_FLAGS.  Also add comments to let
folks know how they can enable it if they really wish to, as suggested
by Craig Ringer.

Author: Michael Paquier, additional comments by me.
Discussion: https://postgr.es/m/CAMsr%2BYGAzcMDOZ_BirnMCL6Sb%3DMUjP0FRE82YBDSbXcf6pm9Yg%40mail.gmail.com

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/e9c81b6016f431af808e4c08191e7aecf034dc80

Modified Files
--------------
src/Makefile.global.in | 3 ++-
src/test/perl/README   | 5 +++++
2 files changed, 7 insertions(+), 1 deletion(-)