[PATCH v2 0/2] libstdc++: Reduce compilation times for chrono-formatting

[Tomasz Kamiński]

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.