util.h etc.: Provide MAX_RAW and MIN_RAW; etc.

util.h etc.: Provide MAX_RAW and MIN_RAW; etc.

MAX and MIN are unsuitable for use where a constant expression is
required.  Provide MAX_RAW and MIN_RAW which are suitable but might
evaluate the left argument twice.

Remove max() in ipaddr.c and replace the call with one to MAX (not
MAX_RAW.  (The old max macro there is operator-priority-unsafe but
there is only one call site and it happens to be OK.)

We ae going to use MAX_RAW later.

No functional change.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>