RFR 8166929: [JVMCI] Expose decompile counts in MDO

[Tom Rodriguez]

http://cr.openjdk.java.net/~never/8166929/webrev
https://bugs.openjdk.java.net/browse/JDK-8166929

This is a minor API addition to expose some of the top-level MDO decompile and recompile counts.  It’s necessary to detect recompilation pathologies.  Tested by printing MDOs from JVMCI.  I also fixed a few problems I discovered with the formatting of the MDO printed form.

tom