MapServer hangs with Apache 2.x

[dmorissette]

This problem was found while working on bug 418, but since this could affect
many users I think it deserves its own bug so that the issue is properly documented.

Apache 2.x has a problem with CGIs that hang when they generate more than 4096
bytes of output to stderr: http://nagoya.apache.org/bugzilla/show_bug.cgi?id=22030

When --enable-debug is enabled MapServer can generate quite a bit of output to
stderr which causes it to hang when running under Apache 2.x.  The current
version is Apache 2.0.47 and the stderr bug is still not fixed so we need to
work around the problem.

Note that this problem does not affect Apache 1.3.x users, it happens only with
Apache 2.x.  This will affect all versions of MapServer but we will implement
the workaround only in 4.0.1 (current stable release) and 4.1 (CVS dev).