Add missing const.
Add model class for representing system information.
Resolve TODO.

- Added GetSystemInfo() to DebuggerInterface. Use that from
  DebugReportGenerator instead of calling get_system_info()/utsname()
  directly since otherwise we'd get the information for the wrong system
  in the eventual case when we have remote debugging support.
Improve tracing.
Add function for creating derived array types.
Implement DwarfType::CreateDerivedArrayType().

Will be used for array typecasting.
Add support for specifying array delimiters.

- Extend CppLanguage::ParseTypeExpression() to also grok array
specifiers. This theoretically lets one now typecast to array types
as well as pointer types, though things don't entirely work as expected
yet.