Move configs out of targets in GN build files.

Move configs out of targets in GN build files.

I'm trying to disallow this since it's confusing. It looks like it provides
scoping for the inner config, but it is actually no different than declaring
the config at the top level. For clarify, all configs and targets should be
declared at the top level.

R=jam@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/7858c0aae5ee449dafe23c0e1aa0c164ae2889eb

[brettw, 2015-08-31 19:43:42]

brettw@chromium.org changed reviewers:
+ jam@chromium.org

[jam, 2015-08-31 20:10:45]

lgtm

[brettw, 2015-08-31 20:45:13]

Committed patchset #1 (id:1) manually as
7858c0aae5ee449dafe23c0e1aa0c164ae2889eb (presubmit successful).