feat(gx): add incomplete 'CGxDeviceGLSDL' (#2)

* chore(build): add vendored SDL 3.0.0 library

* chore(build): add vendored glew-cmake-2.2.0 library

* feat(console): in the presence of -opengl launch flag, change GxApi to OpenGl

* feat(gx): add uncompleted CGxDeviceGLSDL targeting Windows and Linux

* chore(build): change SDL3 linkage from shared (bad) to to static (good)

vendor/sdl-3.0.0/docs/release_checklist.md

@@ -0,0 +1,49 @@
+# Release checklist
+
+When changing the version, run `build-scripts/update-version.sh X Y Z`,
+where `X Y Z` are the major version, minor version, and patch level. So
+`3 8 1` means "change the version to 3.8.1". This script does much of the
+mechanical work.
+
+
+## New feature release
+
+* Update `WhatsNew.txt`
+
+* Bump version number to 3.EVEN.0:
+
+    * `./build-scripts/update-version.sh 3 EVEN 0`
+
+* Do the release
+
+* Update the website file include/header.inc.php to reflect the new version
+
+## New bugfix release
+
+* Check that no new API/ABI was added
+
+    * If it was, do a new feature release (see above) instead
+
+* Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is even)
+
+    * `./build-scripts/update-version.sh 3 Y Z+1`
+
+* Do the release
+
+* Update the website file include/header.inc.php to reflect the new version
+
+## After a feature release
+
+* Create a branch like `release-3.4.x`
+
+* Bump version number to 3.ODD.0 for next development branch
+
+    * `./build-scripts/update-version.sh 3 ODD 0`
+
+## New development prerelease
+
+* Bump version number from 3.Y.Z to 3.Y.(Z+1) (Y is odd)
+
+    * `./build-scripts/update-version.sh 3 Y Z+1`
+
+* Do the release