Flushing logs at exit

There have always been a problem with the log handling in SvxLink that
if an error occurred during startup, the error printouts would not end up
in the log. In fact, nothing would end up in the log, leaving the user
confused. Now the log is flushed before exit so that all printouts end
up in the log.
Paths now set up correctly for ModulePropagationMonitor
Doxygen documentation can now be built using make

The building of Doxygen documentation have now been set up in the CMake
build system. For this there is a new "doc" target. The building of
compressed manual pages now also are only built if the "doc" target is
invoked explicitly. It is also possible to build one specific type of
documentation. The following targets can be used:

  make doc
  make echolib-doc
  make async-doc
  make man
The chat_received TCL function is back

I have now reimplemented the chat_received TCL event handling function
so that it should be secure. Previously it had a serious flaw that could
allow anyone to run commands on the system. Now all characters special
to TCL are escaped. It's still a bit dangerous though. Make sure to
handle the input properly in the chat_received TCL function. Expect
anything...
A bracket was missing in the previous fix
Added a comment about the chat_received function being dangerous
Slightly improved install instructions
Prepared for release 14.08
Added a comment about removing the old buildsystem
Some clean target fixes in the old buildsystem
The Doxygen generated directories are now removed by "make clean"
Fixed a warning which may have made ModuleMetarInfo not work on some arch
Now also building HTML manual pages
Merge branch 'develop' into rtl

Conflicts:
	src/svxlink/ChangeLog
	src/versions