Change clang-format config to allow for two empty lines between functions

BUG=none
R=jkummerow@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/101543002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18226 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

.clang-format

 # Defines the Google C++ style for automatic reformatting.
 # http://clang.llvm.org/docs/ClangFormatStyleOptions.html
 BasedOnStyle: Google
+MaxEmptyLinesToKeep: 2