TC: int _open( const char *path, int access )

	- prototype in io.h, also include fcntl.h

	- this function will not create a file, use _creat() if it doesn't
	  currently exist
	- access is a combination of the following:

		DOS 2.0+ Attributes
		O_RDONLY	open read only
		O_WRONLY	open write only
		O_RDWR	open read/write

		DOS 3.1+ Attributes
		O_NOINHERIT	file is not to be passed to child processes
		O_DENYALL	file is not accessible to others (exclusive)
		O_DENYWRITE	file is read only to all other opens
		O_DENYREAD	file is write only to all other opens
		O_DENYNONE	file is to be shared by all

	- MS C uses _dos_open()
	- see	INT 21,3D   open()   _creat()