[ddbg] Stack trace output format

[Bill Baxter]

Just a suggestion, but I find it is often fairly difficult to locate the 
file and line numbers in the stack traces ddbg spits out.  On a 
standard-width terminal the lines get wrapped around so much that 
generally the filename is split across a newline boundary.

Something to make the file and line numbers stand out more would be 
nice.  Just writing the filename and line number on a line by themselves 
would probably help a lot.  Or perhaps a ddbg flag to turn on some fancy 
ANSI escape sequences to make the important bits appear in 
bold/red/blink mode or something.  It doesn't really matter to me as 
long as they become easier to read.

--bb