Allow clang-format to pass more empty lines

Previously, if you had more than 1 empty line somewhere, clang-format
would eat that empty line. But it is a bit of a pain sometimes to get
the autogenerated code to have the exact empty lines, and there are
valid reasons to allow more than one empty line somewhere, so relax this
condition a bit.

.clang-format

@@ -9,6 +9,7 @@ BreakBeforeBraces: Allman
 BinPackArguments: false
 BinPackParameters: false
 ColumnLimit: 100
+MaxEmptyLinesToKeep: 4
 Standard: Cpp11
 # This requires clang-format 4.0 (at least).
 #FixNamespaceComments: true