pgsql: Set up ar, dlltool, dllwrap, and windres for cross-compiling if

Log Message:
-----------
Set up ar, dlltool, dllwrap, and windres for cross-compiling if necessary.
Plus some makefile cleanup.

part of a patch from Richard Evans

Modified Files:
--------------
    pgsql:
        configure (r1.615 -> r1.616)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/configure?r1=1.615&r2=1.616)
        configure.in (r1.575 -> r1.576)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/configure.in?r1=1.575&r2=1.576)
    pgsql/src:
        Makefile.global.in (r1.247 -> r1.248)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/Makefile.global.in?r1=1.247&r2=1.248)
    pgsql/src/bin/pgevent:
        Makefile (r1.10 -> r1.11)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/pgevent/Makefile?r1=1.10&r2=1.11)
    pgsql/src/interfaces/libpq:
        Makefile (r1.170 -> r1.171)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/libpq/Makefile?r1=1.170&r2=1.171)
    pgsql/src/makefiles:
        Makefile.win32 (r1.11 -> r1.12)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/makefiles/Makefile.win32?r1=1.11&r2=1.12)