make additional tests optional

- Remove them from the MANIFEST as they are
  not supposed to be distributed.
Merge pull request #654 from MartinNowak/optionalTests

[2.065] make additional tests optional
core.sys.posix.fcntl: Fix F_GETLK/F_SETLK/F_SETLKW on Linux/X86_64
Merge pull request #699 from CyberShadow/fcntl64

core.sys.posix.fcntl: Fix F_GETLK/F_SETLK/F_SETLKW on Linux/X86_64
core.sys.windows.windows: Add file locking APIs
core.stdc.stdio: Add MSVCRT functions to convert between fds and HANDLEs
Merge pull request #700 from CyberShadow/windows-locks

core.sys.windows.windows: Add file locking APIs
Merge pull request #701 from CyberShadow/osfhandle

core.stdc.stdio: Add MSVCRT functions to convert between fds and HANDLEs
core.sys.windows.windows: Add ERROR_ALREADY_EXISTS
Merge pull request #702 from CyberShadow/error_already_exists

core.sys.windows.windows: Add ERROR_ALREADY_EXISTS