Version Control With Subversion Source

'pre-lock' hook"), updating the documentation for all hook scripts
while here.

* src/en/book/ch09-reference.xml
(svn.ref.reposhooks.pre-commit): Note the lock-token stdin input to
the pre-commit hook script.
(svn.ref.reposhooks.pre-lock): Update to cover the COMMENT and
STEAL-LOCK inputs, and to describe the lock token dictation (via
stdout) feature.
(svn.ref.reposhooks.pre-unlock): Document the LOCK-TOKEN and
BREAK-UNLOCK parameters.