DynamoRIO build failure on WinXP bot

DynamoRIO build failure on [WinXP bot](http://build.chromium.org/p/client.dynamorio/builders/win-xp-dr).

```
WARNING: next line unrecognized
debug-internal-32: **** 10 build errors ****
157>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
159>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
159>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
161>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
167>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
167>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
204>:E:\b\build\slave\win-xp-dr\build\build_debug-internal-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
225>:..\..\..\..\dynamorio\suite\tests\client-interface\execfault.c(36) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
274>:..\..\..\..\dynamorio\suite\tests\client-interface\annotation-concurrency.c(49) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
275>:..\..\..\..\dynamorio\suite\tests\client-interface\annotation-concurrency.c(49) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
WARNING: next line unrecognized
release-external-32: **** 6 build errors ****
25>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
31>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
31>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
69>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
69>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
70>:E:\b\build\slave\win-xp-dr\build\build_release-external-32\ext\include\droption.h(44) : fatal error C1083: Cannot open include file: 'stdint.h': No such file or directory
vps-debug-internal-32: build successful; no tests for this build
```

Start by reproducing the failure on the WinXP bot and inspect ext\include\droption.h at line 44, where the missing stdint.h include is reported. Compare the debug-internal-32 and release-external-32 build configurations with the successful vps-debug-internal-32 build. Done means the affected WinXP builds complete without the reported stdint.h errors.

Written by the indexing model from the issue text.