clang-format: Don't insert space in __has_include

Before:
  #if __has_include( <strstream>)
  #include <strstream>
  #endif

After:
  #if __has_include(<strstream>)
  #include <strstream>
  #endif

This fixes llvm.org/PR16516.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@189455 91177308-0d34-0410-b5e6-96231b3b80d8