New public API for handling formatters: creating, deleting, modifying categories, and formatters, and managing type/formatter association.
This provides SB classes for each of the main object types involved in providing formatter support:
 SBTypeCategory
 SBTypeFilter
 SBTypeFormat
 SBTypeSummary
 SBTypeSynthetic
plus, an SBTypeNameSpecifier class that is used on the public API layer to abstract the notion that formatters can be applied to plain type-names as well as to regular expressions
For naming consistency, this patch also renames a lot of formatters-related classes.
Plus, the changes in how flags are handled that started with summaries is now extended to other classes as well. A new enum (lldb::eTypeOption) is meant to support this on the public side.
The patch also adds several new calls to the formatter infrastructure that are used to implement by-index accessing and several other design changes required to accommodate the new API layer.
An architectural change is introduced in that backing objects for formatters now become writable. On the public API layer, CoW is implemented to prevent unwanted propagation of changes.
Lastly, there are some modifications in how the "default" category is constructed and managed in relation to other categories.

llvm-svn: 150558