Fix a VPATH build issue - our command lines can sometimes hit the wall
  against the shell's max command line length.  We had a number of needless
  paths included in VPATH builds; this change drops a number of -I'ncluded
  module paths containing no .h files.
  Backport of configure.in r1.251

Reviewed by:	Andre, Justin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@99895 13f79535-47bb-0310-9956-ffa450edef68