Consistently put {} onto the same line for empty functions.

This fixes llvm.org/PR15167.

Before:
LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL()
    : AAAAAAAA(10), BBBBBBBBB(10) {
}
LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL() : AAAAAAAA(10) {}

After:
LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL()
    : AAAAAAAA(10), BBBBBBBBB(10) {}
LLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL() : AAAAAAAA(10) {}