WebGL and iOS GLES version from OF_WEBGL_VERSION / OF_GLES_VERSION defines

[danoli3]

Lets a project pick the WebGL version (emscripten) and the GLES version (iOS / tvOS) with a define instead of editing OF core or main.mm. projectGenerator will expose both as dropdowns and write the define into the project (Xcode preprocessor defines, PROJECT_DEFINES in config.make for make projects).

Emscripten - OF_WEBGL_VERSION=1|2 (default 2)

• ofxAppEmscriptenWindow.cpp: context majorVersion was hardcoded to 2, now OF_WEBGL_VERSION
• config.emscripten.default.mk: OF_WEBGL_VERSION=1 in PROJECT_DEFINES links -s MAX_WEBGL_VERSION=1 -s FULL_ES2, otherwise the existing MAX_WEBGL_VERSION=2 ... FULL_ES3 flags (config.make is included before the platform makefile, so PROJECT_DEFINES is already set there)
• Renderer still sets up as ES 2.0 (setup(2,0)), unchanged, so shaders work for both

iOS / tvOS - OF_GLES_VERSION=1|2|3 (default 2 / ES2)

• ofxiOSConstants.h: #define OF_GLES_VERSION OFXIOS_RENDERER_ES2 unless already defined
• ofiOSWindowSettings default glesVersion uses it (was literal 2)
• ios / tvOS template main.mm: settings.glesVersion = OF_GLES_VERSION;
• Existing projects with OFXIOS_RENDERER_ES2 hardcoded in their main.mm keep ES2 - the define only takes over where main.mm uses it

No define = same behaviour as before on both.

Checks

• em++ compile of ofxAppEmscriptenWindow.cpp with no define and with -DOF_WEBGL_VERSION=1
• makefile filter: empty / OF_WEBGL_VERSION=1 / OF_WEBGL_VERSION=2 resolve to the right -s flags
• iOS SDK clang++ syntax check of ofxiOSConstants.h usage with no define and -DOF_GLES_VERSION=3