Clean up lldb-types.h

Summary:
It defined a couple of types (condition_t) which we don't use anymore,
as we have c++11 goodies now. I remove these definitions.

Also it unnecessarily included a couple of headers which weren't
necessary for it's operation. I remove these, and place the includes in
the relevant files (usually .cpp, usually in Host code) which use them.
This allows us to reduce namespace pollution in most of the lldb files
which don't need the OS-specific definitions.

Reviewers: zturner, jingham

Subscribers: ki.stfu, lldb-commits

Differential Revision: https://reviews.llvm.org/D35113

llvm-svn: 308304