pgsql: MinGW: Link with shell32.dll instead of shfolder.dll.

MinGW: Link with shell32.dll instead of shfolder.dll.

This improves consistency with the MSVC build.  On buildfarm member
narwhal, since commit 846e91e0223cf9f2821c3ad4dfffffbb929cb027,
shfolder.dll:SHGetFolderPath() crashes when dblink calls it by way of
pqGetHomeDirectory().  Back-patch to 9.4, where that commit first
appeared.  How it caused this regression remains a mystery.  This is a
partial revert of commit 889f03812916b146ae504c0fad5afdc7bf2e8a2a, which
adopted shfolder.dll for Windows NT 4.0 compatibility.  PostgreSQL 8.2
dropped support for that operating system.

Branch
------
REL9_4_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/9e02e20ab6df093e1ab751157dfb5c51a420187b

Modified Files
--------------
src/Makefile.global.in               |    5 ++---
src/interfaces/ecpg/ecpglib/Makefile |    5 -----
src/interfaces/libpq/Makefile        |    2 +-
src/interfaces/libpq/win32.mak       |    2 +-
src/port/path.c                      |    8 +++++---
5 files changed, 9 insertions(+), 13 deletions(-)