Make sure it is faster than std::to_value(). And it is, by ~30% for
the normal use case, and much faster when close to the double limits.
util::dtoa also offers a much better precision.
port https://github.com/mapbox/mapbox-gl-js/pull/4781
This improves legibility of labels that follow lines in pitched views.
The previous approach used the limited information in the shader to
calculate put the glyph in approximatelyright place. The new approach
does this more accurately by doing it on the cpu where we have access to
the entire line geometry.
Viewport-aligned curved labels start to look very strange in the distance. Until we have a better system for projecting them, just prevent them from showing.
```
==24942== Conditional jump or move depends on uninitialised value(s)
==24942== at 0x7D943D: mbgl::RenderGeoJSONSource::update(mbgl::Immutable<mbgl::style::Source::Impl>, std::vector<mbgl::Immutable<mbgl::style::Layer::Impl>, std::allocator<mbgl::Immutable<mbgl::style::Layer::Impl> > > const&, bool, bool, mbgl::TileParameters const&) (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x796445: mbgl::RenderStyle::update(mbgl::UpdateParameters const&) (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x77E29D: mbgl::Map::Impl::render(mbgl::View&) (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x77E559: mbgl::Map::Impl::renderStill() (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0xA39772: uv__async_event (async.c:98)
==24942== by 0xA398F8: uv__async_io (async.c:138)
==24942== by 0xA4375F: uv__io_poll (linux-core.c:380)
==24942== by 0xA3A1F2: uv_run (core.c:354)
==24942== by 0x61BADC: API_ZoomHistory_Test::TestBody() (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x89FDE9: void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x885450: testing::Test::Run() (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942== by 0x88642F: testing::TestInfo::Run() (in /home/tmpsantos/Projects/mapbox-gl-native/build/linux-x86_64/Release/mbgl-test)
==24942==
```
