RFR: 7134701 [macosx] Support legacy native library names

[Michael McMahon]

JDK 8 fix for this issue. For readers not familiar with Mac OS, this is to
fix an issue which Apple's JDK 6 supports, but we broke in the jdk 7 
initial port.
The preferred native library file suffix is .dylib on Mac, but some 
legacy libraries
use the suffix .jnilib. Currently openjdk on mac does not recognise the 
.jnilib suffix.

This change is to restore that behavior

http://cr.openjdk.java.net/~michaelm/7134701/webrev.1/

If this change is accepted, we will look for approval to make the same 
change in 7u4.

Thanks,
Michael.