PPAPI generator: Ignore more date-only changes
PPAPI generator: Ignore more date-only changes

Previously, the generator could only ignore changes in the:
// From FILENAME.idl modified DAY MON DATE TIME YEAR.
line if it was not wrapped or wrapped in a specific place. (Note this line
would otherwise change every time you generate).

This CL makes it a little better, in that it will ignore timestamp changes
regardless of where the "modified" output is wrapped. Otherwise, the generator
wants to update a few thunk files because it's now 2015. See:
https://codereview.chromium.org/849473003/
for context.

BUG=
R=bbudge@chromium.org

Review URL: https://codereview.chromium.org/849283003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#311767}

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