- first working stack traces produced with libunwind
- cmake script for finding libunwind
- reverted to old-style Stacktrace interface
- these changes were re-imported from default spring installation
- fixing strange connect problem: client times out waiting for the server to respond
- removed extraneous macro
- removed Hang command (for now)
- fixed a number of tab / ws issues
- sound thread started with Threading::CreateNewThread
- changed the suspend/resume mutex to a semaphore so that its waiters can be counted
- added dev notes file
- fixed cmake script so that libunwind is REQUIRED, plus added error messages for the case where it is not found - it should complain gratuitously if it is not found
Merge remote-tracking branch 'majboredom/threadtrace' into develop

Conflicts:
	rts/Game/LoadScreen.cpp
revert/remove some changes which are unrelated to "libunwind"

(=reduce diff size)
merge error
cleanup build script
- merged abma-develop
- fixed dedicated build requiring Linux-specific source and engineDedicatedLibraries
- added Linux-specific source file Platform/Linux/ThreadSupport.cpp to dedicated
- spring-trace.files is a local IDE file it should not be in git
- fixed Suspend() so that it checks under /proc for verification that a remote thread is actually sleeping
- re-enabled SuspendedStacktrace() calls to Suspend() to support the above
Merge remote-tracking branch 'majboredom/threadtrace' into develop
try to fix travis-ci build
Revert "fix 4413"

This reverts commit eceb7fa13645a2e701e6421663ae456783b94dff.

caused unit jittering / many NP=0