Remove typedefs for MIchar, MIschar, MIuchar.

Summary:
This is a start on bringing lldb-mi more in line with the typical
LLDB coding style. This just removes the usage of the typedefs and
doesn't yet clean up any logic or other issues. (This is to keep
the review simple.)

Reviewers: abidh, ki.stfu, domipheus

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D10917

llvm-svn: 241349