Configure clang-format for KWSys source tree

Use the same format as CMake.  This is the Mozilla style with a few
tweaks:

* Do not align operator arguments.

* Do not always break after a function return type.

* Limit to 79 columns instead of 80 to fit edge cases
  better in 80-column terminals.

* Format for C++98 instead of C++11 because KWSys is written
  in the former language.

Change-Id: I755d3ca9cf2d883e85682fa86cab7127156da861

.clang-format

+---
+# This configuration requires clang-format 3.8 or higher.
+BasedOnStyle: Mozilla
+AlignOperands: false
+AlwaysBreakAfterReturnType: None
+AlwaysBreakAfterDefinitionReturnType: None
+ColumnLimit: 79
+Standard: Cpp03
+...