Fix strings, remove stringify macros, void return types for Consts.h

Fix strings, remove stringify macros, void return types for Consts.h.

Replace multiple #defines of the same strings with externs.
Fix strings mangled by interaction of # and clang-format.
Remove macros as possible.
Make more JS_ functions void and simplify.

R=thestig@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/f9e40aec10263f9445d69598657f42550294d653

[Tom Sepez, 2015-09-11 18:31:25]

Lei, for review. Fixes a few things that bugged me.

[Tom Sepez, 2015-09-11 18:40:34]

On 2015/09/11 18:31:25, Tom Sepez wrote:
> Lei, for review. Fixes a few things that bugged me.
Hang on -- tests coming.

[Tom Sepez, 2015-09-11 19:04:10]

tsepez@chromium.org changed reviewers:
+ thestig@chromium.org

[Tom Sepez, 2015-09-11 19:04:21]

Ok, time for review, Lei.

[Lei Zhang, 2015-09-11 20:04:32]

lgtm

[Tom Sepez, 2015-09-11 20:04:53]

Committed patchset #2 (id:20001) manually as
f9e40aec10263f9445d69598657f42550294d653 (presubmit successful).