* cygwin.din: Export flock.
* flock.c: New file.
* include/sys/file.h: Include sys/cdefs.h.
Add function prototype for flock().
Add some comments from BSD's header for further clarity.
(L_SET, L_CURR, L_INCR, L_XTND): Redefine as the macros
SEEK_SET, SEEK_CUR, SEEK_CUR, & SEEK_END respectively.
(LOCK_SH,LOCK_EX,LOCK_NB,LOCK_UN): New macros for flock().
* include/cygwin/version.h: Bump API minor number.