NAME
	ReadItem - reads a single argument/name from command line (V36)

   SYNOPSIS
	value = ReadItem(buffer, maxchars, input)
	D0                D1        D2      D3

	LONG ReadItem(STRPTR, LONG, struct CSource *)

   FUNCTION
	Reads a "word" from either Input() (buffered), or via CSource, if it
	is non-NULL (see <dos/rdargs.h> for more information).  Handles
	quoting and some '*' substitutions (*e and *n) inside quotes (only).
	See dos/dos.h for a listing of values returned by ReadItem()
	(ITEM_XXXX).  A "word" is delimited by whitespace, quotes, '=', or
	an EOF.

	ReadItem always unreads the last thing read (UnGetC(fh,-1)) so the
	caller can find out what the terminator was.

   INPUTS
	buffer   - buffer to store word in.
	maxchars - size of the buffer
	input    - CSource input or NULL (uses FGetC(Input()))

   RESULT
	value - See <dos/dos.h> for return values.

   BUGS
	Doesn't actually unread the terminator.

   SEE ALSO
	ReadArgs(), FindArg(), UnGetC(), FGetC(), Input(), <dos/dos.h>,
	<dos/rdargs.h>, FreeArgs()