pcre-config --cflags actually emits include paths not cflags, so add it to

correct variable.  Also, reuse APR_INCLUDES/APU_INCLUDES variables so as to
save an extra invocation of config files.

* configure.in: Add PCRE_CONFIG --cflags to INCLUDES; reuse AP{RU}_INCLUDES
  variables.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@731058 13f79535-47bb-0310-9956-ffa450edef68