Move libc-specific code from pg_locale.c into pg_locale_libc.c.

Move implementation of pg_locale_t code for libc collations into
pg_locale_libc.c. Other locale-related code, such as
pg_perm_setlocale(), remains in pg_locale.c for now.

Discussion: https://postgr.es/m/flat/2830211e1b6e6a2e26d845780b03e125281ea17b.camel@j-davis.com

Author: jeff-davis

src/backend/utils/adt/Makefile

@@ -80,6 +80,7 @@ OBJS = \
 	partitionfuncs.o \
 	pg_locale.o \
 	pg_locale_icu.o \
+	pg_locale_libc.o \
 	pg_lsn.o \
 	pg_upgrade_support.o \
 	pgstatfuncs.o \

src/backend/utils/adt/meson.build

@@ -67,6 +67,7 @@ backend_sources += files(
   'partitionfuncs.c',
   'pg_locale.c',
   'pg_locale_icu.c',
+  'pg_locale_libc.c',
   'pg_lsn.c',
   'pg_upgrade_support.c',
   'pgstatfuncs.c',