Fix PR rust/20110

Fix PR rust/20110

PR rust/20110 concerns the type of an integer constant that is too
large for "i32", the default integer type.  This patch changes the
type of such a constant to i64.  This is important because such values
are often addresses, so truncating them by default is unfriendly.

Built and regtested on x86-64 Fedora 23.

2016-06-10  Tom Tromey  <tom@tromey.com>

	PR rust/20110:
	* rust-exp.y (lex_number): Don't truncate large numbers to i32.

2016-06-10  Tom Tromey  <tom@tromey.com>

	PR rust/20110:
	* gdb.rust/expr.exp: Add test for integer constant larger than
	i32.