Refactoring: moved function 'x_malloc' to reduce dependencies.
Refactoring: encapsulation and handling of global variables regarding NMEA log window into the class NMEALogWindow.
Removed import of unused global variables in datastream.cpp
NMEALogWindow is now a real singleton.
TTYWindow no longer operates on global variables. Size and Position are being handled fewer times, still consistent. Reduction of dependencies.
Merge pull request #50 from mariokonrad/refactor

Refactoring: use of global variables reduced for NMEA log/debug window, dependencies reduced