Most of our private headers need to be treated as submodules so that
Clang modules can export things correctly. Previous commits that split
monolithic headers into smaller chunks were unaware of this requirement,
and so this is being addressed in one fell swoop. Moving forward, most
new headers will need to have their own submodule (anything that's
conditionally included is exempt from this rule, which means `__support`
headers aren't made into submodules).
This hasn't been marked NFC, since I'm not 100% sure that's the case.
Differential Revision: https://reviews.llvm.org/D103551
Implements part of P0896 'The One Ranges Proposal'.
Implements [range.iter.op.next].
Depends on D101922.
Differential Revision: https://reviews.llvm.org/D102563
Petr Hosek