Changed configuration to actually work with a displaced source tree.

Changed configuration to actually work with a displaced source tree.
Major changes, but localized...

	* configure.in: redo "autoconf frobbage" since the old way didn't
	work with srcdir. Now, AC_OUTPUT generates all three Makefiles,
	and ISODEMAKEFILE is subst'ed in to be either Makefile.isode or
	Makefile.sane. EXTRA_RULES_IN is used to append the extra stuff to
	the end of the "real" one of the two.
	* configure.in: krb5_encode.h and krb5_encode.h are source, not
	generated, so use CopySrcHeader instead.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@3939 dc483132-0cff-0310-8789-dd5450dbe970