native readme update
model uart dependency on posix
remove trailing newlines
remove superfluous uart USEMODULEs from examples
remove superfluous uart USEMODULEs from test
update test_shell/ReadMe.txt
Merge pull request #634 from LudwigOrtmann/uart_posix_dep

uart related cleanup
fix changed checking order to avoid possible access violation
added typecast for starck_start in native
added typecast for starck_start in arm_cpu to ensure correct calculation
added typecasts for the used send/receive buffer pointer buff
Merge pull request #624 from LudwigOrtmann/native_readme_update

native readme update
Merge pull request #649 from BytesGalore/fix_missing_typecasts

Fix added missing typecasts to stack (arm/msba2) and send/receive buffer (native)
Merge pull request #648 from BytesGalore/fix_possible_access_violation_transceiver

fix changed checking order to avoid possible access violation