PR libgcj/29178:
	* gnu/java/nio/charset/US_ASCII.java (Encoder.canEncode): New method.
	(Encoder.canEncode): Likewise.
	(Encoder.encodeLoop): Return unmappable for all non-ASCII characters.
	* gnu/java/nio/charset/ByteCharset.java (Encoder.canEncode): New
	method.
	(Encoder.canEncode): Likewise.
	* gnu/java/nio/charset/ISO_8859_1.java (Encoder.canEncode): New
	method.
	(Encoder.canEncode): Likewise.

From-SVN: r117209