Generalize the dcc_{r,x}_argv routines so they can be used to
transfer arbitrary array-of-strings tokens (useful for protocol
hacking experiments; no functional change).

tested and reviewed by cheepero@gmail.com, to address
<http://code.google.com/p/distcc/issues/detail?id=36>
"distcc-mon-gnome displays multiple rows for same host/slot".

Optional GSS-API Functionality.

This patch implements mutual authentication, out of sequence and
replay detection using the GSS-API.  The changes implemented are
optional and are turned off by default.

This option is specified to the client through an environment variable
as is the name of the server principal to authenticate.  Currently
the server principal can be left unspecified and a default based on
the host keytab will be used.

This option is specified to the daemon through a command line option,
with the name of the principal whose credentials the daemon should
use specified as an environment variable.  A simple handshake is
exchanged between the client and server in order to prevent
unecessary delays and protocol derailments when mixing authenticating
and non-authenticating clients and servers.

Revised based on review comments.
GSS-API authentication is now implemented as a per host option.

Revised further by me (Fergus Henderson) to fix a spelling error
and to rename the per host option from ",gssapi" to ",auth".

add a new "--scan-includes" option to distcc which shows
which headers distcc would send to the remote machine in
pump mode, without actually compiling anything.

<http://code.google.com/p/distcc/issues/detail?id=9>:

use S_ISLNK and S_ISDIR macros, to make the code more readable.

Reviewers: Craig Silverstein

(typically the only change is in the FSF street address).  Add Google
copyright line in some places it was missing.  Add GPLv2 notice to
avahi patches.

OKed by fergus

Currently, our users get the following error message when their workstation is
not in the allowed domains as specified in the server configuration:

distcc[20742] (dcc_readx) ERROR: unexpected eof on fd5
distcc[20742] (dcc_r_token_int) ERROR: read failed while waiting for token "DONE"

With this change, a message explains some likely causes of the problem.

Also, fix the emacs var-setting line: it was missing a semicolon
before, which means the entire line was being ignored.

No contentful change.

Reviewed by fergus@google.com

lines.  Fixed up resulting mis-indented code I noticed (mostly in
files that used 8 space indents, or used 4-space and 8-space indents
in the same file (!)).  Added the emacs tab-var setting for all files,
not just some of them.

I also added in copyright notices for files I noticed that didn't have
them.  We'll want to do another pass-through to fix these up properly,
though.

I used the following perl snippet to check for mis-indented code after
converting tabs to whitespace:

  $ for i in *.{c,h}; do echo $i; perl -nle 'if ($indent > 0) {$sp=" " x $indent; /^$sp[^ ]/ && print "$.: $_"; $indent=0;}; if (/^( *).*{/ ) {$indent=length($1);} else {$indent=0;}' $i; done | less

It had false positives, but hopefully didn't miss anything.

Reviewed by klarlund@google.com