pgsql: Add #include postgres_fe.h in two win32-specific files, because

Log Message:
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Add #include postgres_fe.h in two win32-specific files, because there is
pg-specific code in those files, or might be some day.

Modified Files:
--------------
    pgsql/src/interfaces/libpq:
        pthread-win32.c (r1.11 -> r1.12)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/pthread-win32.c.diff?r1=1.11&r2=1.12)
        win32.c (r1.17 -> r1.18)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/win32.c.diff?r1=1.17&r2=1.18)