Add the Data Inspection Language (DIL) implementation pieces for
handling plain local and global variable names.
See https://discourse.llvm.org/t/rfc-data-inspection-language/69893 for
information about DIL.
This change includes the basic AST, Lexer, Parser and Evaluator pieces,
as well as some tests.
ValueObject is part of lldbCore for historical reasons, but conceptually
it deserves to be its own library. This does introduce a (link-time) circular
dependency between lldbCore and lldbValueObject, which is unfortunate
but probably unavoidable because so many things in LLDB rely on
ValueObject. We already have cycles and these libraries are never built
as dylibs so while this doesn't improve the situation, it also doesn't
make things worse.
The header includes were updated with the following command:
```
find . -type f -exec sed -i.bak "s%include \"lldb/Core/ValueObject%include \"lldb/ValueObject/ValueObject%" '{}' \;
```
