Instead of arbitrary division of headers into include and include/krb5, with

Instead of arbitrary division of headers into include and include/krb5, with
include directives sometimes using krb5/foo.h and sometimes using foo.h, and
-I options always given for both directories in both source and build trees,
push include/krb5/* up a level and drop the krb5 directory (except, for the
moment, the change log).

Updated #include directives, -I options, and dependencies accordingly, and
deleted one or two bits of old, unused code that was noticed in the process.

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@17730 dc483132-0cff-0310-8789-dd5450dbe970