(vc-bzr-with-process-environment, vc-bzr-std-process-invocation): New macros.

(vc-bzr-with-process-environment, vc-bzr-std-process-invocation): New macros.
(vc-bzr-command, vc-bzr-command*): Use them.
(vc-bzr-with-c-locale): Remove.
(vc-bzr-dir-state): Replace its use with vc-bzr-command.
(vc-bzr-buffer-nonblank-p): New function.
(vc-bzr-state-words): New const.
(vc-bzr-state): Look for `bzr status` keywords in output.
Display everything else as a warning message to the user.
Fix status report with bzr >= 0.15.