clang-format: Don't remove space between #elif and parentheses.

Before:
  #elif(AAAA && BBBB)

After:
  #elif (AAAA && BBBB)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@245043 91177308-0d34-0410-b5e6-96231b3b80d8