Don't link support/* against systemd libs.

* Makefile.in: Link httpd using $(HTTPD_LIBS).

* configure.in: Add systemd to HTTPD_LIBS rather than LIBS.  Add PCRE
  libs to HTTPD_LIBS.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1528034 13f79535-47bb-0310-9956-ffa450edef68