Use DefWindowProc for the initial SDL window proc #15

Job	Run time
Create test plan	6s
level1 / Haiku	2m 6s
level2 / Android (Gradle)	2m 50s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	3m 42s
level2 / FreeBSD	3m 4s
level2 / MacOS (Framework) (arm64)	4m 54s
level2 / Steam Linux Runtime 3.0 (arm64)	2m 23s
level2 / Steam Linux Runtime 3.0 (x86_64)	3m 8s
level2 / Nintendo 3DS	2m 24s
level2 / MacOS (GNU prefix)	7m 5s
level2 / Windows (msys2, ucrt64)	10m 1s
level2 / iOS (CMake & xcode)	2m 57s
level2 / Ubuntu (latest)	8m 27s
level2 / Windows (MSVC, clang-cl x64)	5m 54s
level2 / Windows (msys2, mingw32)	11m 21s
level2 / NetBSD	3m 0s
level2 / Sony PlayStation 2	6m 9s
level2 / LoongArch64	3m 27s
level2 / Ubuntu 24.04 (ARM64)	6m 7s
level2 / Ubuntu 22.04 (Intel Compiler)	6m 1s
level2 / Sony PlayStation Portable	3m 56s
level2 / GDK (MSVC, x64)	3m 7s
level2 / OpenBSD	6m 19s
level2 / MacOS (Framework) (x64)	4m 3s
level2 / Android (Android.mk)	1m 29s
level2 / Windows (msys2, clang64)	8m 37s
level2 / Windows (MSVC, clang-cl x86)	6m 59s
level2 / Ubuntu 22.04	5m 20s
level2 / N-Gage	5m 3s
level2 / Ubuntu 22.04 (Intel oneAPI)	8m 3s
level2 / Windows (MSVC, x64)	5m 50s
level2 / MacOS 26 (Framework) (arm64)	4m 23s
level2 / Emscripten	10m 44s
level2 / Windows (MSVC, x86)	5m 52s
level2 / Android (CMake, lean)	4m 47s
level2 / Windows (msys2, mingw64)	10m 28s
level2 / RISC OS	1m 32s
level2 / Android (CMake)	4m 47s
level2 / PowerPC	2m 35s
level2 / PowerPC64	2m 21s
level2 / Sony PlayStation Vita (GLES w/ pib)	3m 6s
level2 / Windows (MSVC, ARM64)	3m 58s
level2 / tvOS (CMake & xcode)	4m 46s
	3h 33m 11s

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