Testcase for fortran/PR3743 "Reference to intrinsic `ISHFT' invalid".

[David Edelsohn]

        i3 = ISHFT(i,BIT_SIZE(i))
             ^
Reference to intrinsic `ISHFT' at (^) invalid -- one or more arguments have incorrect type

	I just updated the PR information in GNATS.  The failure (at least
on PowerPC) is due to G77 considering BIT_SIZE a function returning REAL.
Fortran's implicit type rules make a function beginning with the letter
'B' default to type REAL which is not valid as the second argument to
ISHFT.

	I am not familiar enough with G77 parsing to know when BIT_SIZE is
suppose to be recognized as an intrinsic instead of a function call.
Given that this behaves differently on different platforms, I suspect
there is something non-deterministic in the parser.

David