Make source map location information more readable.

Make source map location information more readable.

This changes "file:1:2" to "line 1, column 2 of file" and ":1:2" to
"line 1, column 2" in [SourceFile.getLocationMessage]. The more
machine-readable colon-separated format doesn't make sense for a
message intended for humans.

Since [Location.formatString] seems more likely to be consumed by
machines, its format was left as-is.

This also prepares version 0.9.1 for release.

This was previously submitted as r36603. That caused buildbot errors and was
rolled back by r36615. This CL fixes the test errors in r36603.

R=sigmund@google.com

Committed: https://code.google.com/p/dart/source/detail?r=36717

[nweiz, 2014-05-27 21:29:05]

The actual source_map package is unchanged from the original CL. The only real
changes are to csslib.

I plan to release csslib 0.10.0+1 once this CL lands.

[Siggi Cherem (dart-lang), 2014-05-27 22:46:49]

lgtm

[nweiz, 2014-05-27 23:01:29]

Committed patchset #1 manually as r36717 (presubmit successful).