investigate XP test failures: client.events, client.drsysm_test, etc.

_From [bruen...@google.com](https://code.google.com/u/109494838902877177630/) on June 21, 2013 18:19:30_

after fixing issue #1195 the xp bot still needs some work: http://build.chromium.org/p/client.dynamorio/builders/win-xp-dr/builds/307/steps/pre-commit%20suite/logs/summary%3A%2016%20failed%2C%201%20flaky%20failed debug-i32-static-ext: build successful; no tests for this build
debug-internal-32: 118 tests passed, ***\* 16 tests failed, of which 1 were flaky: ****
unit_tests
code_api|security-common.selfmod
code_api|security-common.retnonexisting => Application E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\suite\tests\bin\security-common.retnonexisting.exe (3428). Internal Error Internal DynamoRIO Error: ......\dynamorio\core\vmareas.c:8003 !ok || !TEST(MEMPROT_WRITE, prot2) || TEST(FRAG_SELFMOD_SANDBOXED, *flags)
code_api|client.events
code_api|client.events_cpp
code_api|client.large_options
code_api|client.drsyms-test
code_api|client.pcache-use => Application E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\suite\tests\bin\client.pcache.exe (2424). Internal Error Internal DynamoRIO Error: ......\dynamorio\core\perscache.c:1593 tag != NULL || (instr_opcode_valid(instr) instr_is_cbr(instr))
code_api|sample.instrcalls
code_api|api.startstop => Application E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\suite\tests\bin\api.startstop.exe (2900). Internal Error Internal DynamoRIO Error: ......\dynamorio\core\dispatch.c:749 ks-depth 2 stop_not_matching not allowed to clear kstack
code_api,opt_memory|client.events
code_api,disable_traces|client.events
code_api,opt_speed|client.events
code_api,thread_private,disable_traces|client.events
code_api,thread_private|client.events
code_api|client.nudge_ex_FLAKY
release-external-32: build successful; no tests for this build
vps-debug-internal-32: build successful; no tests for this build

_Original issue: http://code.google.com/p/dynamorio/issues/detail?id=1196_