Fix incorrect register-number range check.

For the JVMTI Get/SetLocalVariable functions we were checking the slot
number as though it was unsigned when in fact it is held as a (signed)
jint.

Test: ./art/tools/run-libjdwp-tests.sh --mode=host
Test: ./test.py --host
Change-Id: I9bbc0054ae48884cd8ddf84b5cbd60d5247bf43b
10 files changed