* common.din: Export GetCommandLine{A,W}.

* common.din: Export GetCommandLine{A,W}.
* kernel32.cc: Add includes needed for GetCommandLine functions.
(ucmd): New function.
(cygwin_GetCommandLineW): Ditto.
(cygwin_GetCommandLineA): Ditto.
* spawn.cc (child_info_spawn::worker): Rename one_line -> cmd.  Use lb_wcs
macro to generate a wide character version of the line buffer.  Remove
duplicate printing of command line.  Don't access members of linebuf directly.
* winf.h: Use pragma once.
(linebuf): Make storage private.
(linebuf::operator size_t): New operator.  Return size of buf.
(linebuf::operator wchar_t): New operator.
(linebuf::wcs): New function.
(lb_wcs): New macro.
* include/cygwin/version.h: Bump API minor number to 268.
* strfuncs.cc: Clarify descriptive file comment.