Doxygen: only generate documentation for [Objective-]C[++] files.

Doxygen was generating some pretty bogus-looking documentation for
the Python http_transport_test_server, making it look like a C++
namespace and generating mostly useless documentation:

http://docs.crashpad.googlecode.com/git/doxygen/annotated.html

R=rsesek@chromium.org

Review URL: https://codereview.chromium.org/706233003

crashpad.doxy

@@ -774,7 +774,7 @@ INPUT_ENCODING         = UTF-8
 # *.md, *.mm, *.dox, *.py, *.f90, *.f, *.for, *.tcl, *.vhd, *.vhdl, *.ucf,
 # *.qsf, *.as and *.js.
 
-FILE_PATTERNS          =
+FILE_PATTERNS          = *.c *.cc *.h *.m *.mm
 
 # The RECURSIVE tag can be used to specify whether or not subdirectories should
 # be searched for input files as well.