Unicode support on Win32.

Win32 API calls that are Unicode aware require wide character
strings, but LLDB uses UTF8 everywhere.  This patch does conversions
wherever necessary when passing strings into and out of Win32 API
calls.

Patch by Cameron
Differential Revision: http://reviews.llvm.org/D17107
Reviewed By: zturner, amccarth

llvm-svn: 264074