pgsql: Make ECPG regression tests use native threading instead of

Log Message:
-----------
Make ECPG regression tests use native threading instead of pthreads, now that
 ecpglib supports it.
Change configure (patch from Bruce) and msvc build system to no longer require
 pthreads on win32, since all parts of postgresql can be thread-safe using the
 native platform functions.

Modified Files:
--------------
    pgsql:
        configure (r1.539 -> r1.540)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.diff?r1=1.539&r2=1.540)
        configure.in (r1.506 -> r1.507)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in.diff?r1=1.506&r2=1.507)
    pgsql/doc/src/sgml:
        install-win32.sgml (r1.37 -> r1.38)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/install-win32.sgml.diff?r1=1.37&r2=1.38)
    pgsql/src/interfaces/ecpg/test/expected:
        thread-thread.c (r1.11 -> r1.12)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-thread.c.diff?r1=1.11&r2=1.12)
        thread-thread_implicit.c (r1.11 -> r1.12)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-thread_implicit.c.diff?r1=1.11&r2=1.12)
    pgsql/src/interfaces/ecpg/test/thread:
        thread.pgc (r1.2 -> r1.3)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/thread/thread.pgc.diff?r1=1.2&r2=1.3)
        thread_implicit.pgc (r1.2 -> r1.3)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/thread/thread_implicit.pgc.diff?r1=1.2&r2=1.3)
    pgsql/src/tools/msvc:
        Mkvcbuild.pm (r1.6 -> r1.7)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Mkvcbuild.pm.diff?r1=1.6&r2=1.7)
        Project.pm (r1.10 -> r1.11)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Project.pm.diff?r1=1.10&r2=1.11)
        Solution.pm (r1.19 -> r1.20)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Solution.pm.diff?r1=1.19&r2=1.20)
        config.pl (r1.5 -> r1.6)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/config.pl.diff?r1=1.5&r2=1.6)