pgsql: Move relpath() to libpgcommon

Move relpath() to libpgcommon

This enables non-backend code, such as pg_xlogdump, to use it easily.
The previous location, in src/backend/catalog/catalog.c, made that
essentially impossible because that file depends on many backend-only
facilities; so this needs to live separately.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/a73018392636ce832b09b5c31f6ad1f18a4643ea

Modified Files
--------------
src/backend/Makefile | 8 +-
src/backend/access/rmgrdesc/smgrdesc.c | 1 +
src/backend/access/rmgrdesc/xactdesc.c | 1 +
src/backend/access/transam/xlogutils.c | 1 +
src/backend/catalog/catalog.c | 140 +---------------------------
src/backend/commands/tablespace.c | 1 +
src/backend/storage/buffer/bufmgr.c | 1 +
src/backend/storage/buffer/localbuf.c | 1 +
src/backend/storage/file/fd.c | 1 +
src/backend/storage/file/reinit.c | 1 +
src/backend/storage/smgr/md.c | 1 +
src/backend/utils/adt/dbsize.c | 1 +
src/backend/utils/adt/misc.c | 1 +
src/backend/utils/cache/relcache.c | 1 +
src/common/Makefile | 11 ++-
src/common/relpath.c | 162 ++++++++++++++++++++++++++++++++
src/include/catalog/catalog.h | 20 ----
src/include/common/relpath.h | 41 ++++++++
src/tools/msvc/Mkvcbuild.pm | 11 ++-
19 files changed, 237 insertions(+), 168 deletions(-)