Add .clang-format and .dir-locals.el files to set coding style

Configure emacs and clang-format 15 to the coding style I am choosing
for qpdf.

.clang-format

@@ -0,0 +1,50 @@
+# -*- yaml -*-
+# This configuration works with clang-format-15.
+# See https://clang.llvm.org/docs/ClangFormatStyleOptions.html
+---
+Language: Cpp
+BasedOnStyle: LLVM
+AlignAfterOpenBracket: AlwaysBreak
+AlignEscapedNewlines: DontAlign
+AlignOperands: DontAlign
+AllowShortFunctionsOnASingleLine: None
+AlwaysBreakAfterReturnType: AllDefinitions
+AlwaysBreakTemplateDeclarations: Yes
+AttributeMacros:
+  - QPDF_DLL
+  - QPDF_DLL_CLASS
+BinPackArguments: false
+BinPackParameters: false
+BraceWrapping:
+  AfterClass:      true
+  AfterFunction:   true
+  AfterNamespace:  true
+  AfterStruct:     true
+  AfterUnion:      true
+BreakBeforeBraces: Custom
+BreakConstructorInitializers: AfterColon
+DeriveLineEnding: false
+PackConstructorInitializers: Never
+IncludeCategories:
+  - Regex:           '^["<](qpdf)/'
+    Priority:        1
+    SortPriority:    0
+    CaseSensitive:   false
+  - Regex:           '.*'
+    Priority:        2
+    SortPriority:    0
+    CaseSensitive:   false
+  - Regex:           '.*'
+    Priority:        1
+    SortPriority:    0
+    CaseSensitive:   false
+IndentCaseBlocks: true
+IndentExternBlock: Indent
+IndentPPDirectives: AfterHash
+IndentWidth: 4
+InsertTrailingCommas: Wrapped
+KeepEmptyLinesAtTheStartOfBlocks: false
+NamespaceIndentation: All
+PointerAlignment: Left
+PPIndentWidth: 1
+SpaceBeforeInheritanceColon: false

.dir-locals.el

@@ -0,0 +1,38 @@
+((nil . ((indent-tabs-mode . t)
+         (qpdf-cc-style
+          .
+          ("qpdf"
+           (c-basic-offset . 4)
+           (c-comment-only-line-offset . 0)
+           (c-offsets-alist
+            (defun-block-intro . +)
+            (block-open . 0)
+            (substatement-open . 0)
+            (statement-cont . +)
+            (case-label . 0)
+            (access-label . -2)
+            (statement-case-intro . +)
+            (statement-case-open . +)
+            (arglist-intro . +)
+            (arglist-close . 0)
+            (inline-open . 0)
+            (inlambda . 0)
+           )
+          )
+         )
+         (c-noise-macro-names . ("QPDF_DLL" "QPDF_DLL_CLASS" "QPDF_DLL_LOCAL"))
+        )
+ )
+ (c++-mode . ((eval . (progn
+                        (add-to-list 'c-style-alist qpdf-cc-style)
+                        (c-set-style "qpdf")
+                      )
+              ))
+ )
+ (c-mode . ((eval . (progn
+                      (add-to-list 'c-style-alist qpdf-cc-style)
+                      (c-set-style "qpdf")
+                    )
+            ))
+ )
+)

TODO

@@ -60,43 +60,11 @@ Use clang-format-15.
 
   as well as the use of a comment to force a line break.
 
-Tentative .clang-format:
+https://clang.llvm.org/docs/ClangFormatStyleOptions.html
-
-```
----
-Language:        Cpp
-BasedOnStyle:  LLVM
-AlignAfterOpenBracket: AlwaysBreak
-AlignEscapedNewlines: DontAlign
-AllowShortFunctionsOnASingleLine: None
-BinPackArguments: false
-BinPackParameters: false
-BreakConstructorInitializers: BeforeComma
-DeriveLineEnding: false
-PackConstructorInitializers: Never
-IncludeCategories:
-  - Regex:           '^["<](qpdf)/'
-    Priority:        1
-    SortPriority:    0
-    CaseSensitive:   false
-  - Regex:           '.*'
-    Priority:        2
-    SortPriority:    0
-    CaseSensitive:   false
-  - Regex:           '.*'
-    Priority:        1
-    SortPriority:    0
-    CaseSensitive:   false
-IndentCaseBlocks: true
-IndentWidth:     4
-InsertTrailingCommas: Wrapped
-KeepEmptyLinesAtTheStartOfBlocks: false
-PointerAlignment: Left
-```
 
 Remaining work:
 
-* Try to get emacs c-style to match as closely as possible
+* Document .dir-locals.el and how it's close but not perfect
 * Consider blame.ignoreRevsFile if it seems to help
 * Add a `make format` similar to `make spell` (or whatever this ends
   up being with cmake)