mechanism more flexible, but otherwise should not affect your build
even if you regenerate the "configure" script.
(Most likely you need to run bootstrap.sh as you really need to re-run
autoheader for reasons that i do not completely understand).

If you don't regenerate "configure", of course you will see no difference.

In detail:

- restructure the check for mandatory modules to remove some
  redundant code blocks;

- extend the AST_EXT_LIB_CHECK so that it can used also for
  checking headers;

- define the AST_C_DEFINE_CHECK macro to test for #defined symbols;

- for the two above macros, add a last argument that getscopied into
  HAVE_$1_VERSION so the source can adapt to different versions of the
  same libraries/header/etc

- document the above;

- document a problem that existed before and i did not manage to solve:
  the 'description' argument to AC_DEFINE does not substiture shell variables
  so you will not see the actual values in the comments (in autoconfig.h)..




git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@44467 65c4cc65-6c06-0410-ace0-fbb531ad65f3