`-t timeout`; fix #4, alternative solution re #2.

Adds new flag `-t timeout milliseconds`, to stop long-running vcprompt
invocatoins.

`vcprompt -t 20` is recommended usage.

TODO:

* respect -f in how the result should printed on a timeout job.
Fix inconsistent whitespace.
- no space between function name and "("
- space between function parameters
- exactly one blank line between functions
If we're going to ignore errors from strtol(), do it right.
Clarify timeout-related help and output a smidge.
Also rename msalarm() to set_alarm(), because that's what it does.
Update contributor list, copyright dates.
Style consistency: always put function return types on their own line.
Style consistency: format pointers like the rest of the C universe.
Instead of "type* name", use "type *name".
Merge from bitbucket.org/gward/vcprompt

Conflicts:
	src/common.h
	src/svn.c
	src/vcprompt.c