ClassLevel and Class.level have been unused for (at least) years.
This CL removes them.
Library.flags furthermore had the first bit unused after the 'external'
flag was removed (last year I think).
This CL shifts it down so the actual flags doesn't start at bit 1.
Change-Id: Ie0afd150cad331ea694bc5fe2a20aafed22916cc
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/169202
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Jens Johansen <jensj@google.com>
Jens Johansen
2928af2b12