RFR(S) More collection set and matrix cleanup

[Zhengyu Gu]

A few more cleanup on collection set and matrix:

1) Use jbyte instead of char
2) Make both classes more self-contained: moved memory allocation into 
the constructors.
3) Inline cset test functions


Webrev: 
http://cr.openjdk.java.net/~zgu/shenandoah/cset_matrix_refactor/webrev.00/


Test: hotspot_gc_shenandoa: fastdebug and release


Thanks,

-Zhengyu