... as well as some cleanup (some commented-out code is left to
support UxTradMsg again is someone really complains ;)).

- saved gettimeofday() calls in imtcp (and increased reception buffer)
- somewhat optimized stringbuf.c
- some other optimizations

... this provides some basic support to integrate extensions that
are not direct parts of rsyslog to be built during its build
process.

Conflicts:
	ChangeLog

... as well as some other minor issues.

Conflicts:
	tests/Makefile.am

Conflicts:
	tests/Makefile.am

The imdiag module now can very effectively inject messages, which also
frees us from uncertainties of tcp reception and processing. All shell
script based tests have been modularized, what makes it far easier to
create new tests. Also, the test bench now executes more reliable and
much faster, because we can now rely on actual engine information where
we previously did just a dumb sleep.