Enhance stacktrace to report column numbers

Author: mgreter

src/backtrace.cpp

@@ -24,6 +24,8 @@ namespace Sass {
         ss << indent;
         ss << "on line ";
         ss << trace.pstate.line + 1;
+        ss << ":";
+        ss << trace.pstate.column + 1;
         ss << " of " << rel_path;
         // ss << trace.caller;
         first = false;
@@ -33,6 +35,8 @@ namespace Sass {
         ss << indent;
         ss << "from line ";
         ss << trace.pstate.line + 1;
+        ss << ":";
+        ss << trace.pstate.column + 1;
         ss << " of " << rel_path;
       }