clang-format.bash: update to clang-format-6.0

Update `.clang-format` with configuration to make the 6.0 format as
close as possible to what 3.8 produced before.  Then revise the style to
indent preprocessor directives (a feature new since 3.8).

Author: bradking

.clang-format

@@ -1,9 +1,21 @@
 ---
-# This configuration requires clang-format 3.8 or higher.
+# This configuration requires clang-format version 6.0 exactly.
 BasedOnStyle: Mozilla
 AlignOperands: false
-AlwaysBreakAfterReturnType: None
+AllowShortFunctionsOnASingleLine: InlineOnly
 AlwaysBreakAfterDefinitionReturnType: None
+AlwaysBreakAfterReturnType: None
+BinPackArguments: true
+BinPackParameters: true
+BraceWrapping:
+  AfterClass:      true
+  AfterEnum:       true
+  AfterFunction:   true
+  AfterStruct:     true
+  AfterUnion:      true
+BreakBeforeBraces: Custom
 ColumnLimit: 79
-Standard: Cpp11
+IndentPPDirectives: AfterHash
+SortUsingDeclarations: false
+SpaceAfterTemplateKeyword: true
 ...

src/clang-format.bash

@@ -78,8 +78,8 @@ test "$#" = 0 || die "$usage"
 
 # Find a default tool.
 tools='
+  clang-format-6.0
   clang-format
-  clang-format-3.8
 '
 if test "x$clang_format" = "x"; then
     for tool in $tools; do