Only request C++11 when compiling C++ code.

Only request C++11 when compiling C++ code.

Linux pdfium builds have 215 warnings of this form:
command line option -std=gnu++11 is valid for C++/ObjC++ but not for C

The obvious fix is to not request C++11 for C compilations. The only
complication was the the switch we are using is actually gnu++0x, not
gnu++11.

BUG=https://code.google.com/p/pdfium/issues/detail?id=102
R=tsepez@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/c4457a8f623bb4f09542d98bdde9c33ca932c4a3

[brucedawson, 2015-01-09 00:59:32]

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

[Tom Sepez, 2015-01-09 18:51:00]

Bless you sir. LGTM.

[brucedawson, 2015-01-09 19:51:13]

Committed patchset #1 (id:1) manually as
c4457a8f623bb4f09542d98bdde9c33ca932c4a3 (presubmit successful).