r516: On GNU/Linux distributions which allow to use both 2.4 and 2.6 kernels

r516: On GNU/Linux distributions which allow to use both 2.4 and 2.6 kernels
there is SYS_utimes syscall defined at compile time in glibc-kernheaders but
it is available on 2.6 kernels only. Therefore, we can't rely on syscall at
compile time but have to check that behaviour during program execution. An easy
workaround is to have replacement for utimes() implemented within our wrapper and
do not rely on syscall at all. Thus, if REPLACE_UTIME is defined already (by packager),
skip these syscall shortcuts.
(This used to be commit e278e2e6e095b1c01eab307d55edf2cde48dcba2)