RFC: mmap override patch #2

[Chris Robinson]

An updated attempt at the mmap override patch that I previously sent. This 
version properly uses a signed type for the mmap wrapper (as off_t/off64_t are 
signed types), fixes a few things with the munmap wrapper relating to 
truncated and sliced file_views, and implements a mremap wrapper for Linux.

There's some debugging stuff left in the mremap wrapper since I have yet to 
catch anything that uses it, particularly using ERR instead of TRACE and an 
explicit abort() call so it isn't missed. There's also a %lld formatter in the 
mmap wrapper that will be fixed later.

I'd be interested to hear how well it does or doesn't work, as well as any 
comments or critiques on the code.