GN: Add logging for the location of an invocation.

GN: Add logging for the location of an invocation.

I was working on the Windows build and having problems finding why a file was loaded that shouldn't have been. This adds the source of the invocation to the verbose logging so you can find this information.

I removed an assert which caused a debug assertion for random punctuation and isn't harmful (a real error will be reported).

I moved the location-to-string conversion code into the location class so I can share it for my new logging command, and moved a bunch of other logging functions to the new .cc file.

BUG=288991
R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=223469

[scottmg, 2013-09-16 20:13:05]

lgtm

[brettw, 2013-09-16 23:31:45]

Committed patchset #2 manually as r223469 (presubmit successful).