Add a .clang-format file implementing the Icinga 2 style guide

.clang-format

@@ -0,0 +1,25 @@
+---
+BasedOnStyle: LLVM
+AccessModifierOffset: -4
+AlignAfterOpenBracket: DontAlign
+BreakBeforeBraces: Mozilla
+ColumnLimit: 100
+IncludeCategories:
+  - Regex: ^"(base|icinga|remote|test)/
+    Priority: 1
+    CaseSensitive: false
+  - Regex: ^<boost/
+    Priority: 2
+    CaseSensitive: false
+  - Regex: ^<
+    Priority: 3
+    CaseSensitive: false
+IndentCaseLabels: true
+IndentWidth: 4
+PenaltyBreakAssignment: 50
+PenaltyBreakBeforeFirstCallParameter: 50
+PenaltyBreakOpenParenthesis: 50
+PointerAlignment: Left
+ReferenceAlignment: Left
+TabWidth: 4
+UseTab: Always

.gitignore

@@ -3,6 +3,7 @@
 
 # Except those related to git and vagrant
 !.git*
+!.clang-format
 !.puppet*
 !.travis.yml
 !.mailmap