Make PPAPI headers compilable with -Wstrict-prototypes

Make PPAPI headers compilable with -Wstrict-prototypes

This changes the PPAPI headers to use "foo(void)" rather than "foo()"
in function prototypes and definitions.

In C (but not C++), "foo()" declares a function with unspecified
arguments, which allows foo to be called with excess arguments or
implemented with excess arguments.  Using "foo(void)" is more correct
and will prevent such mistakes.  GCC's -Wstrict-prototypes warning
requires using "foo(void)", and we'd like to turn this warning on for
NaCl C code.

BUG= https://code.google.com/p/nativeclient/issues/detail?id=3114
TEST= rerun ppapi/generators/generator.py + compile

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=170120

[brettw, 2012-11-29 00:26:37]

lgtm