Make struct k5buf less opaque and get rid of k5buf-int.h.  Make it
easy to initialize a k5buf in an error state so that it can be freed
in a cleanup handler.  Add a function k5_buf_status which returns 0 or
ENOMEM.  Remove k5_buf_data and k5_buf_len.  Rename k5_free_buf to
k5_buf_free.  Adjust all callers to match.

Include autoconf.h (either directly or via proxy) before system
headers, so that feature test macros defined there can affect the
system namespace.  Where include order was changed, eliminate some
redundant or unnecessary includes.

ticket: 7961

krb5int_c_combine_keys is used only by SAM-2 preauth with neither the
send-encrypted-sad nor use-sad-as-key flags, so it isn't covered by
any automated function tests.  Add some unit tests to make sure that
it works and returns the expected results for two randomly generated
test vectors.

ticket: 7914
target_version: 1.12.2
tags: pullup

Remove uitypes.h and just include stdint.h; all we need from it is
uint{8,16,32}_t.

Also add a testing interface to allow weak iteration counts.
(Published test vectors use weak iteration counts.)

ticket: 7465
target_version: 1.12
tags: pullup

Provide default values in pre.in for PROG_LIBPATH, PROG_RPATH,
SHLIB_DIRS, SHLIB_RDIRS, and STOBJLISTS so that they don't have to be
specified in the common case.  Rename KRB5_RUN_ENV and KRB5_RUN_VARS
to RUN_SETUP (already the most commonly used name) and RUN_VARS.  Make
sure to use DEFINES for local defines (not DEFS).  Remove some other
unnecessary makefile content.

Caught by ASan.

Rename the krb5int_buf_ family of functions to use the k5_ prefix for
brevity.  Reformat some k5buf implementation code to match current
practices.