Added a bit of imjournal documentation.

	new file:   imjournal.html
doc: integrate imjournal doc contribution into rest of doc system
build: add cached copies of generated man pages to dist tarball

This solves problems with some build environments.
cosmetic: reduce compiler warning

init variable that does not really need to be initialized, as it
is immediately overwritten - but the compiler is not smart enough
to see that
Fix a condition in imjournal

This prevented state file from being written with newer systemd.
Add some more debug information.
Add missing pid part of syslog tag.
doc: add recent patches to ChangeLog
Add a check for the rst2man binary

Called when either libgcrypt or GuardTime is enabled.
bugfix: .logsig files had tlv16 indicator bit at wrong offset