pgsql: Remove lc_collate_is_c().

Remove lc_collate_is_c().

Instead just look up the collation and check collate_is_c field.

Author: Andreas Karlsson
Discussion: https://postgr.es/m/60929555-4709-40a7-b136-bcb44cff5a3c@proxel.se

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/06421b08436414b42cd169501005f15adee986f1

Modified Files
--------------
src/backend/access/spgist/spgtextproc.c |  2 +-
src/backend/commands/collationcmds.c    |  8 ++------
src/backend/utils/adt/like_support.c    |  4 ++--
src/backend/utils/adt/pg_locale.c       | 33 +++-----------------------------
src/backend/utils/adt/selfuncs.c        |  6 ++++--
src/backend/utils/adt/varchar.c         | 20 ++++++-------------
src/backend/utils/adt/varlena.c         | 34 ++++++++++++++++-----------------
src/include/utils/pg_locale.h           |  1 -
8 files changed, 35 insertions(+), 73 deletions(-)