GENC should always export composite names

RFC 6680 requires that gss_export_name_composite begin the output
token with 04 02.  So we must produce a composite token even if the
name has no authdata, and be able to consume a composite token with no
authdata attributes.

[ghudson@mit.edu: expanded commit message]

ticket: 7400 (new)
Add Python scripts to check for C style issues

util/cstyle-file.py checks a file for C style issues and displays
line-by-line output.  It is not terribly sophisticated, and can
probably be improved upon (e.g. by doing an emacs batch-reindent of
the file and checking for differences in indentation).

util/cstyle.py produces diffs using git, runs the file checker on each
modified C source file in each diff, and displays the output lines
attribute to the diff.
Fix a couple of typos
Add an input ccache get-init-creds option

Add a krb5_get_init_creds_opt_set_in_ccache() function.  An input
ccache may hold configuration data which the client libraries can
use to influence their decisions.
Use octal escapes for non-printable parts of {str}/{lenstr}/{data}

When adding {str}, {lenstr}, or {data} to trace output, scan for
bytes which might be non-printable, and add them as octal-escaped
versions of themselves if any are found.
Add a -C flag to dump configuration entries
Add "pa_types" configuration to ccaches

* When producing preauth data, keep track of the types of padata which
  the module that produced the data can handle.  Originally this was
  just the type of data we'd produced, but that caused problems for
  PKINIT.
* After obtaining credentials, store that list of preauth types as a
  "pa_types" configuration item in the out_ccache.
* Read a list of allowed preauth types from an in_ccache, if possible.
* If we have a list of allowed preauth types, skip any "real" modules
  which aren't in that list.
Test in_ccache and pa_types functionality.

* Add a krb5int_build_conf_principals() function to allow our get/set
  code to directly prune out duplicate config entries.
* Verify that when we specify pa_types, they affect whether or not we
  will use a particular preauth mechanism.
* Verify that we correctly save the list of preauth mechanisms that are
  used in out_ccaches.
Add "pa_config_data" configuration to ccaches

* Read a "pa_config_data" item from an in_ccache, if provided, and add a
  callback which client preauth plugins can use to retrieve a string
  value that's keyed by a string.
* Add a callback which client preauth plugins can use to provide string
  key/value pairs to be stored in the ccache.
Use config storage for client identity selection

* Keep track of the names of client identities when we load them.
* Store the client identity we just used when we create or retry a
  client request.
* If we read a client identity from the configuration, treat it like the
  KDC does: pick the "this is it, there is no other" logic branch.
Use config storage for client token selection

* Save the vendor name of the token we used to create the challenge.
* If we saved the name of a token vendor previously, prune out any
  tokeninfos which contain different vendor names.
Misc fixes for anonymity and crypto agility

* Agility fix: don't try to free an uninitialized keyblock.
* Anonymity: don't try to sign data when we have no signer specified,
  and don't try to add signed attributes then, either.  Don't bail on
  unsigned data: just note that it's not signed, since that's expected
  now, and carry on.
* Reset the prompt_types list immediately after the prompter callback
  returns, as is done elsewhere.
* Use a temporary variable to hold the chain-inclusion setting for CMS.
* Whitespace tweaks.
* Print a debug message if we're unable to locate the matching private
  key for a certificate when we've just loaded both of them from PEM
  files.
* Create an NSS context for use when performing KDF, so that the tests,
  which call into the function directly, will work.
project page draft; do not merge