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/glew-cmake-2.2.0/config/Makefile.darwin-gcc6

@@ -0,0 +1,31 @@
+# For building with Brew gcc:
+# $ brew install gcc
+GLEW_DEST = /usr/local
+NAME = $(GLEW_NAME)
+CC = gcc-6
+LD = gcc-6
+CFLAGS.EXTRA += -dynamic -fno-common
+CFLAGS.EXTRA += -fPIC
+# Lots of warnings with -pedantic
+# warning: ISO C forbids conversion of object pointer to function pointer type
+#CFLAGS.EXTRA += -pedantic
+LDFLAGS.EXTRA =
+ifneq (undefined, $(origin GLEW_APPLE_GLX))
+CFLAGS.EXTRA += -std=c99
+CFLAGS.EXTRA += -I/usr/X11R6/include -D'GLEW_APPLE_GLX'
+LDFLAGS.GL = -L/usr/X11R6/lib -lGL -lX11
+else
+CFLAGS.EXTRA += -std=c89
+GLEW_NO_GLU = -DGLEW_NO_GLU
+LDFLAGS.GL = -framework OpenGL
+endif
+LDFLAGS.STATIC =
+LDFLAGS.DYNAMIC =
+WARN = -Wall -W
+POPT = -Os
+BIN.SUFFIX =
+LIB.SONAME    = lib$(NAME).$(SO_MAJOR).dylib
+LIB.DEVLNK    = lib$(NAME).dylib
+LIB.SHARED    = lib$(NAME).$(SO_VERSION).dylib
+LIB.STATIC    = lib$(NAME).a
+LDFLAGS.SO    = -dynamiclib -install_name $(GLEW_DEST)/lib/$(LIB.SHARED) -current_version $(SO_VERSION) -compatibility_version $(SO_MAJOR)