Refine & simplify the interBreak mechanism

Replace dvmUpdateInterpBreak() and friends with more direct
enable/disable subMode calls.  Hide breakFlags manipulation from
higher-level callers and infer what is needed from the active
subMode.

Add documentation to the interpreter control section of
mterp/README.txt

Change-Id: If7ebee5d8e4db8154c4caed72cf89ec088045998
15 files changed