Show the line number for syntax errors in preset files

[Dakon]

What steps will reproduce the problem?

1. Create a custom MapCSS file with syntax error
2. activate it in JOSM
3. the error is printed, but no hint where in the file it is

What is the expected result?

A easy way to identify the exact point of the error should be printed, preferably the line number, or the XML hierarchy to the object.

What happens instead?

Only the direct anchestor node is shown, which can occur multiple times in the preset.

Please provide any additional information below. Attach a screenshot if possible.

Repository Root: http://josm.openstreetmap.de/svn
Build-Date: 2015-03-30 01:30:55
Last Changed Author: stoecker
Revision: 8159
Repository UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Relative URL: ^/trunk
URL: http://josm.openstreetmap.de/svn/trunk
Last Changed Date: 2015-03-29 14:37:50 +0200 (Sun, 29 Mar 2015)
Last Changed Rev: 8159

Identification: JOSM/1.5 (8159 de) Linux openSUSE 13.1 (Bottle) (x86_64)
Memory Usage: 407 MB / 910 MB (315 MB allocated, but free)
Java version: 1.7.0_55, Oracle Corporation, OpenJDK 64-Bit Server VM
Java package: java-1_7_0-openjdk:x86_64-1.7.0.55

Plugins:
- OpeningHoursEditor (30962)
- buildings_tools (30955)
- geochat (31056)
- imagery_offset_db (31056)
- jna (30892)
- log4j (30892)
- native_password_manager (31061)
- osmarender (30892)
- pbf (31010)
- poly (31056)
- public_transport (30892)
- reverter (30990)
- terracer (30892)
- undelete (30892)
- utilsplugin2 (31040)