include <sys/types.h> & <sys/mkdev.h> directly for major() and minor()

Linux seems to pick these up via another header, but Solaris needs them
explicitly included, or we get undefined symbol errors for major & minor.

v2: use headers documented in makedev(3C) man page instead of sysmacros.h

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

v3 [Emil Velikov]: include sys/mkdev.h only when available.
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>