pgsql: Make sure -D is an absolute path when starting server on Windows

Make sure -D is an absolute path when starting server on Windows.

This is needed because Windows services may get started with a different
current directory than where pg_ctl is executed. We want relative -D
paths to be interpreted relative to pg_ctl's CWD, similarly to what
happens on other platforms.

In support of this, move the backend's make_absolute_path() function
into src/port/path.c (where it probably should have been long since)
and get rid of the rather inferior version in pg_regress.

Kumar Rajeev Rastogi, reviewed by MauMau

Branch
------
master

Details
-------
http://git.postgresql.org/pg/commitdiff/9aca51250681d2e8d18ed1d73e7cd1283d1cf303

Modified Files
--------------
src/backend/utils/init/miscinit.c | 71 ------------------------
src/bin/pg_ctl/pg_ctl.c | 14 ++++-
src/include/miscadmin.h | 1 -
src/include/port.h | 1 +
src/port/path.c | 111 ++++++++++++++++++++++++++++++++++++-
src/test/regress/pg_regress.c | 27 ---------
6 files changed, 124 insertions(+), 101 deletions(-)