[foreign] RFR 8221471: jextract source genarator generates non-compilable classes with naming clashes

[Sundararajan Athijegannathan]

Please review.

Bug: https://bugs.openjdk.java.net/browse/JDK-8221471
Webrev: https://cr.openjdk.java.net/~sundar/8221471/webrev.02/index.html

Current naming scheme: Header interfaces are named as "foo". Static 
forwarder class is named as "foo_h"
New naming scheme: Header interfaces are named as "foo_h". Static 
forwarder class is named as "foo_lib"

Thanks,
-Sundar