clang-format: indent continued lines (KhronosGroup#739)

This addresses comments from recent PR reviews.

Signed-off-by: Kevin Petit <[email protected]>

Author: kpet

.clang-format

@@ -53,7 +53,7 @@ CommentPragmas:  '^ IWYU pragma:'
 CompactNamespaces: false
 ConstructorInitializerAllOnOneLineOrOnePerLine: false
 ConstructorInitializerIndentWidth: 4
-ContinuationIndentWidth: 0
+ContinuationIndentWidth: 4
 Cpp11BracedListStyle: false
 DerivePointerAlignment: true
 DisableFormat:   false