Static non-PIE binaries always have a base address of 0 (even if the ELF

Static non-PIE binaries always have a base address of 0 (even if the ELF
headers start at a higher address).  Using the wrong base address meant
that we were protecting the wrong address range for the malloc internals
which made the code error out now that mimmutable(2) no longer allows an
RW->R transition.  Issue found by gkoehler@ who got most of the way
towards a proper fix.

ok deraadt@