Completely revamp configure so that it preserves the standard make

Completely revamp configure so that it preserves the standard make
variables CPPFLAGS, CFLAGS, CXXFLAGS, LDFLAGS and LIBS by moving
the configure additions to EXTRA_* variables.  Also, allow the user
to specify NOTEST_* values for all of the above, which eliminates the
need for THREAD_CPPFLAGS, THREAD_CFLAGS, and OPTIM.  Fix the setting
of INCLUDES and EXTRA_INCLUDES.  Check flags as they are added to
avoid pointless duplications.  Fix the order in which flags are given
on the compile and link lines.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@88960 13f79535-47bb-0310-9956-ffa450edef68