add clang-format configuration file for the unittest tree

---

Language:        Cpp

BasedOnStyle:  LLVM

AccessModifierOffset: -4

AlignEscapedNewlines: Left

AllowShortFunctionsOnASingleLine: Inline

AllowShortLambdasOnASingleLine: None

AllowShortIfStatementsOnASingleLine: WithoutElse

BraceWrapping:

  AfterFunction:   true

BreakBeforeBraces: Custom

BreakInheritanceList: AfterColon

BreakConstructorInitializers: AfterColon

ColumnLimit:     100

IndentCaseLabels: true

IndentWidth:     4

ObjCBlockIndentWidth: 4

PenaltyBreakAssignment: 4

Standard:        Cpp11

TabWidth:        4

UseTab:          Never

...