Add source location breakpoints to repl

this commit add the ability to set a  breakpoints by specifying the file name, the line number and (optional) the column number of the source code.

While it work, it is not very polish.

The error handling is sloppy.
It does no path canonization.
I have not update the UI the advertise the capability.
There are no path auto-completion.

In other word, it still is a prototype, but it work.

examples/repl.rs

@@ -398,9 +398,21 @@ mod example {
         if let Some(addr) = parse_address(location).or(parse_symbol(&location, context)) {
             Ok(vec![addr])
         } else {
-            Err(format!(
+            if let Some(source_location) = parse_source_location(location) {
+                Ok(context
+                    .debuginfo
+                    .as_ref()
+                    .unwrap() // this unwrap cannot fail due to the call to load_debuginfo_if_necessary
+                    .find_location_addr(&source_location)
+                    .unwrap() // todo: this unwrap could fail if the debugee contain invalid debug info.
+                    .into_iter()
+                    .map(|(_, addr)| addr as usize)
+                    .collect())
+            } else {
+                Err(format!(
                     "Breakpoints must be set on a symbol or at a given address. For example `b main` or `b 0x0000555555559394` or even `b 93824992252820`"
                 ))?
+            }
         }
     }
 
@@ -427,6 +439,27 @@ mod example {
         context.debuginfo().get_symbol_address(&location)
     }
 
+    fn parse_source_location(location: &str) -> Option<addr2line::Location> {
+        use addr2line::Location;
+
+        let mut iter = location.split(":");
+        let file = iter.next();
+        let line = iter
+            .next()
+            .map_or(None, parse_address)
+            .map_or(None, |num| NonZeroU32::new(num as u32));
+        let column = iter
+            .next()
+            .map_or(None, parse_address)
+            .map_or(None, |num| NonZeroU32::new(num as u32));
+
+        if let (Some(file), Some(line)) = (file, line) {
+            Some(Location { file, line, column })
+        } else {
+            None
+        }
+    }
+
     fn show_backtrace(context: &mut Context, bt_type: &BacktraceType) -> CrabResult<()> {
         let call_stack: Vec<_> = get_call_stack(context, bt_type)?;
         for func in call_stack {