windows: handle WM_POINTERCAPTURECHANGED events, fix maybe-undefined behavior. #3471

Job	Run time
Create test plan	5s
level1 / Haiku	2m 2s
level2 / Sony PlayStation Portable	3m 56s
level2 / MacOS (Framework) (x64)	5m 16s
level2 / Windows (msys2, mingw32)	9m 8s
level2 / Ubuntu 22.04	4m 49s
level2 / Ubuntu 20.04	4m 12s
level2 / RISC OS	1m 27s
level2 / Windows (MSVC, ARM)	4m 5s
level2 / LoongArch64	3m 1s
level2 / Sony PlayStation 2	5m 9s
level2 / Android (Gradle)	2m 32s
level2 / Ubuntu 20.04 (Intel oneAPI)	6m 28s
level2 / GDK (MSVC, x64)	1m 38s
level2 / Windows (msys2, ucrt64)	8m 36s
level2 / Steam Linux Runtime (Sniper)	2m 50s
level2 / FreeBSD	2m 32s
level2 / MacOS (GNU prefix)	3m 34s
level2 / Emscripten	9m 18s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	3m 21s
level2 / Sony PlayStation Vita (GLES w/ pib)	3m 18s
level2 / PowerPC	1m 49s
level2 / Android (CMake, lean)	2m 49s
level2 / NetBSD	2m 38s
level2 / Windows (MSVC, clang-cl x86)	5m 47s
level2 / Nintendo 3DS	2m 11s
level2 / Windows (msys2, clang64)	6m 7s
level2 / tvOS (CMake & xcode)	2m 11s
level2 / Windows (MSVC, x64)	5m 50s
level2 / Ubuntu 20.04 (Intel Compiler)	4m 32s
level2 / Android (Android.mk)	1m 21s
level2 / Windows (msys2, clang32)	7m 34s
level2 / Android (CMake)	3m 2s
level2 / iOS (CMake & xcode)	2m 12s
level2 / Windows (MSVC, x86)	5m 37s
level2 / PowerPC64	1m 52s
level2 / Windows (MSVC, clang-cl x64)	5m 27s
level2 / MacOS (Framework) (arm64)	2m 11s
level2 / Windows (MSVC, ARM64)	4m 19s
level2 / Windows (msys2, mingw64)	8m 11s
	2h 42m 57s

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