[ddbg] Unable to find source files

[Bill Baxter]

I ran into a problem the other day where ddbg 0.8.1 was telling me that 
it couldn't find line xxx of file yyy.  But it knew there was a file 
yyy.  It listed it in the modules list.

Don't have time to narrow it down to a repro right now, but just wanted 
to see if anyone else had seen this.  The source file in question was 
called OptMesh.d and I was running the debugger from a \data directory 
beneath that.  It was finding the other files fine, so my thought was 
maybe there's a bug with mixed case filenames.  The files that were 
working were all lowercase.  Maybe just a coincidence, though.

--bb