pgsql: Rename CACHE_LINE_SIZE to PG_CACHE_LINE_SIZE.

Rename CACHE_LINE_SIZE to PG_CACHE_LINE_SIZE.

As noted in http://bugs.debian.org/763098 there is a conflict between
postgres' definition of CACHE_LINE_SIZE and the definition by various
*bsd platforms. It's debatable who has the right to define such a
name, but postgres' use was only introduced in 375d8526f290 (9.4), so
it seems like a good idea to rename it.

Discussion: 20140930195756(dot)GC27407(at)msg(dot)df7cb(dot)de

Per complaint of Christoph Berg in the above email, although he's not
the original bug reporter.

Backpatch to 9.4 where the define was introduced.

Branch
------
REL9_4_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/f78319fec8eb8aed34d6e1e43ca35fb0a9bfe108

Modified Files
--------------
src/backend/access/transam/xlog.c | 4 ++--
src/include/pg_config_manual.h | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)