JDK 9 RFR of 8058679: More bad characters in BigIntegerTest

[Brian Burkhalter]

Hello bad characters,

Issue:	https://bugs.openjdk.java.net/browse/JDK-8058679
Webrev:	http://cr.openjdk.java.net/~bpb/8058679/webrev.00/

Tested with "-encoding US-ASCII” passed to javac.

Thanks,

Brian