Add pretty printing of Clang "bitfield" enums
Using enumerators as flags is standard practice. This patch adds
support to LLDB to display such enum values symbolically, eg:
(E) e1 = A | B
If enumerators don't cover the whole value, the remaining bits are
displayed as hexadecimal:
(E) e4 = A | 0x10
Detecting whether an enum is used as a bitfield or not is
complicated. This patch implements a heuristic that assumes that such
enumerators will either have only 1 bit set or will be a combination
of previous values.
This patch doesn't change the way we currently display enums which the
above heuristic would not consider as bitfields.
Reviewers: jingham, labath
Differential Revision: https://reviews.llvm.org/D67520