pgsql: Use snprintf instead of wsprintf, and use getenv("APPDATA")

Log Message:
-----------
Use snprintf instead of wsprintf, and use getenv("APPDATA") instead of
SHGetFolderPath.

This removes the direct dependency on shell32.dll and user32.dll, which
eats a lot of "desktop heap" for each backend that's started. The
desktop heap is a very limited resource, causing backends to no
longer start once it's been exhausted.

We still have indirect depdendencies on user32.dll through third party
libraries, but those can't easily be removed.

Dave Page

Modified Files:
--------------
    pgsql/src/backend/port/win32:
        signal.c (r1.18 -> r1.19)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/signal.c?r1=1.18&r2=1.19)
    pgsql/src/port:
        kill.c (r1.8 -> r1.9)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/kill.c?r1=1.8&r2=1.9)
        path.c (r1.71 -> r1.72)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/port/path.c?r1=1.71&r2=1.72)