Make code compile with clang_use_chrome_plugin (part I)

This change contains files in core/fpdfapi directory. This is part
of the efforts to make PDFium code compilable by Clang chromium
style plugins.

The changes are mainly the following:
-- move inline constructor/destructor of complex class/struct out-of-line;
-- add constructor/destructor of complex class/struct if not
   explicitly defined;
-- add explicit out-of-line copy constructor when needed;
-- move inline virtual functions out-of-line;
-- Properly mark virtual functions with 'override';
-- some minor cleanups;

BUG=pdfium:469

Review-Url: https://codereview.chromium.org/2060973002

0 files changed, 0 insertions, 0 deletions