* fix libc prototypes of offsets to have correct integer sizes and
signedness. This gets all behavior tests to pass for
armv8-linux-musleabihf
* fix linux mmap syscall to have correct integer size and signedness
for offset
* disable failing armv8-linux-musleabihf std lib tests. See 3289. I
suspect compiler-rt issue. Note these tests fail with this target
triple regardless of whether musl is actually linked (-lc).
This effectively takes one-bit from the length field and uses it as the
sign bit. It reduces the size of an Int from 40 bits to 32 bits on a
64-bit arch.
This also reduces std.Rational from 80 bits to 64 bits.
