Fix a handling of full path in break-insert.

For some time, eclipse (CDT) uses full path of the file in break-insert command
when putting breakpoint on a source line. On windows, a typical command looks
like the following.
56-break-insert -f F:\\work\\ws\\test\\main.c:49

Current implementation in lldb-mi have problem in 2 ways.
1. It was assuming that there will be only one : in the path which is wrong if full
path is supplied.
2. CDT sends out path with double backslashes in windows which gives error on 
resolution.

Fixed the : issue in lldb-mi. Changed FileSpec::Normalize to make sure that it
handles the path with \\ correctly. Added test cases to check for full path in
both lldb-mi and lldb. Also added a test case to check SBFileSpec with double
slashes.

llvm-svn: 228538