Require clang-format 9 and reformat source code

This updates the lint script to require clang-format 9 and reformats
existing source code. Since VS2019 ships with clang-format 9 this
should make auto reformats less painful.

This also updates the clang-format configuration to set
BraceWrapping.AfterCaseLabel to true to ensure consistent brace
style; otherwise clang-format 9+ defaults to putting braces on
the same line as switch case labels.

Source/.clang-format

@@ -20,6 +20,7 @@ AlwaysBreakTemplateDeclarations: true
 BinPackArguments: true
 BinPackParameters: true
 BraceWrapping:
+  AfterCaseLabel:  true
   AfterClass:      true
   AfterControlStatement: true
   AfterEnum:       true