Add ability to disable overdraw shaders

[brunoabinader]

#5371 and #5534 add a second set of shaders for overdraw mode. We should completely disable this with ifdefs or so when we're building a release build for publication to avoid additional shader compilation overhead. Overdraw mode is a debugging tool and shouldn't be in the SDK.

/cc @brunoabinader

[brunoabinader]

Disabling overdraw implies in actually disabling debug options in general - 👍 for including https://github.com/mapbox/mapbox-gl-native/blob/master/include/mbgl/map/map.hpp#L171-L174 inside those ifdefs?

[brunoabinader]

Moved discussion about debug options in release mode to #5699.

[brunoabinader]

Node render test debug/overdraw fails because we are running the render tests on a Travis node build bot in release mode. @mikemorris any objections on switching this bot to debug mode?

[mikemorris]

@brunoabinader 👍 to BUILDTYPE=Debug on that bot

[brunoabinader]

@1ec5 @mikemorris could you please 👀 on the changelog changes before 🚢 ?

[1ec5]

Nit: remove this blank line.

[1ec5]

For iOS and macOS, can you mark the enum values with __attribute__((deprecated("…"))); and point out that they're no-ops in the documentation comment? You can condition the deprecated attribute on the DEBUG build variable.

If you think it's still useful to have these options in iosapp, you can conditionally compile the code that adds and carries out the action. For macosapp, change the menu item's validation code to conditionally return YES for debug and NO otherwise.

[1ec5]

If deprecation and conditional compiling is too much trouble, it'd be fine to simply document the two enum options as being nonfunctional.