Add support for source line + column breakpoints

Most debuggers support setting a breakpoint using a file name and line number.

Some debuggers also support setting a breakpoint using a file name, line number and a column number.

Specifying a column number allows breaking in a specific sub-expression or function call.

It would be nice if Qt Creator supported that.

The only C++ / native code debugger that supports that at the moment is lldb (from what i know).

$ lldb
help breakpoint set
....
-u <column> ( --column <column> )
            Specifies the column number on which to set this breakpoint.

gdb has an open bug report to add support, cdb/msvc i didn't find anything in the documentation.

There are other language debuggers that support column breakpoints, like javascript, typescript, powershell. It might be relevant for future Debugger Adapter protocol support.

Here's a video of what the UX for column breakpoints looks like in visual studio code.

https://github.com/microsoft/vscode/issues/14784#issuecomment-278299633

And a screenshot.

I know it's a long shot, but i figured i'd file a report anyway.