Issue 3656: Problems building Lilypond 2.17.95 with libc++ for use with llvm

std-vector.hh did not include config.hh but relied on it
Issue 3656/2: disambiguate our own ::to_string from std::to_string
Revert "optimal-page-breaking: signed/unsigned bug; issue 1553"

This reverts commit 7e771a83cafb00e0ed58400a93b728e283c4ad9c.
Issue 3672: NR: a few typos in connection with paper size