RFR: (bulk) Fix build failures on Mac OS

[Aleksey Shipilev]

http://cr.openjdk.java.net/~shade/shenandoah/try-macos-fix/webrev.01/

This is a bulk fix train, please review in bulk. I shall commit them as separate changesets. Brief
tour of changes:

*) alloc-seq-uint.patch: {first|last}_alloc_seq_num() are actually uint64_t, not size_t;
*) hr-switches.patch: some compilers do not like switches that do not claim all enums;
*) verifier-liveness.patch: some compilers do not like implicit size_t casts;
*) for-loops.patch: some compilers do not like empty for-loop bodies;

Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey