This is now series of two patches, that aim to reduce compilation times for chrono formatting: * first patch implements formatting of chrono types in terms of single _ChronoData type, instead of instantiating it for all calendar types * second patch deduplicates localized chrono formatting code, by putting it into the main formatting loop.
Tested on x86_64-linux locallt. The std/time* test passed with -D_GLIBCXX_USE_CXX11_ABI=0 and -D_GLIBCXX_DEBUG.
