i#1308,i#2216,i#2752,i#2694: mark more tests as flaky (#2760)
i#1308,i#2216,i#2752,i#2694: mark more tests as flaky (#2760)

An attempt to make Travis and Appveyor greener:

Issue #1308, #2216: marks security-common.decode-bad-stack _FLAKY.

Issue #2752: marks 32-bit api.detach_spawn _FLAKY.

Issue #2694: makes tool.histogram.offline tiny only for 32-bit Windows.
AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio,AmesianX/dynamorio