17.5.2 Changed Makefiles

Add `@CFLAGS@', `@CPPFLAGS@', and `@LDFLAGS@' in your Makefile.in files, so they can take advantage of the values of those variables in the environment when configure is run. Doing this isn't necessary, but it's a convenience for users.

Also add `@configure_input@' in a comment to each input file for AC_OUTPUT, so that the output files contain a comment saying they were produced by configure. Automatically selecting the right comment syntax for all the kinds of files that people call AC_OUTPUT on became too much work.

Add config.log and config.cache to the list of files you remove in distclean targets.

If you have the following in Makefile.in:

     prefix = /usr/local
     exec_prefix = $(prefix)

you must change it to:

     prefix = @prefix@
     exec_prefix = @exec_prefix@

The old behavior of replacing those variables without `@' characters around them has been removed.