Add .clang-format file

This file can be used to reformat FreeType sources and commits
using one of these methods:

- Direct formatting of a whole file:

    clang-format -i path/to/file

  For example, to reformat all sources at once:

    echo builds/unix/ftconfig.h.in $(git ls-files *.[hc]) | xargs clang-format -i

- Only reformat the changed lines in the current work directoy:

    git clang-format

The style settings in this file are very close to the FreeType
formatting style, with the following exceptions which are not supported
here:

- Mminimal 2-space margin on each non-empty line.
  (no left margin instead).

- 2 empty lines between variable declarations and statements in C blocks.
  (only 1 is kept).

    {
      int  x = ...;

      foo(x);
    }

  becomes

    {
      int x = ...;

      foo(x);
    }

- Aignment of declarations uses 2 spaces to separate types and variable
  names (only 1 space is kept).

     int  x;    =>   int x;
     int  y;         int y;

- The start used for output parameters in function signature should be
  near the variable name (always near the type).

    void foo(int* input_ptr, int *output_ptr)
      => void foo(int* input_ptr, int* output_ptr)

.clang-format

@@ -0,0 +1,16 @@
+BasedOnStyle: Chromium
+AlignAfterOpenBracket: Align
+AlignConsecutiveAssignments: true
+AlignConsecutiveDeclarations: true
+AlignConsecutiveMacros: true
+AlignEscapedNewlines: true
+# AlignOperands: Align
+AlignTrailingComments: true
+AlwaysBreakAfterReturnType: AllDefinitions
+BreakBeforeBraces: Allman
+ColumnLimit: 80
+DerivePointerAlignment: false
+IndentCaseLabels: false
+PointerAlignment: Left
+SpaceBeforeParens: ControlStatements
+SpacesInParentheses: true