"fix" validation test
fix clang compile warning:
comparison of constant ... with expression of type ... is always true
minor NLC
UnitDefs: print the error message when unitdef creation fails
allow to set default host ip / default port by config,
allow port 0 (=random):

fix #4473
adjust error message / print bound port number
remove ouput of empty log lines:
LOG() already adds \n
if() ... elseif() ... elseif() -> switch/case
Fix aircraft FPS mode

Don't ignore being in FPS mode when there's no input (fly straight instead)
Merge pull request #116 from sprunk/patch-3

Fix aircraft FPS mode
fix #4475 (refactoring mistake in 5f9d050)
warning -> error when configured joystick can't be found
fix some cppcheck warnings:
initialization in initialization list.
fix cppcheck warnings