RFR (M): 8220301: Remove jbyte use in CardTable (affects all platforms)

[Thomas Schatzl]

Hi all,

 can I have reviews for this change the replaces the use of the JNI
data type jbyte in the CardTable class by uint8_t via the custom
CardValue typedef?

This cleanup stems from trying to get rid of JNI data types in VM/GC
code; formerly the main reason to use them here has been that the
Atomic operations were not available for e.g. uint8_t, but that has
been fixed for a long time.

While the change itself is a no-op in practice, and testing showed so,
I would like non-Oracle platform maintainers to try to compile the
change and report problems because of lack of build platforms.

CR:
https://bugs.openjdk.java.net/browse/JDK-8220301
Webrev:
http://cr.openjdk.java.net/~tschatzl/8220301/webrev/
Testing:
hs-tier1-5

Thanks,
  Thomas