Changes:
* Fix redundant REX.W prefix on JMP reg64.
* Make the behaviour of -O0 match NASM 0.98 legacy behavior.
* -w-user can be used to suppress the output of %warning directives.
* Fix bug where ALIGN would issue a full alignment datum instead of
zero bytes.
* Fix offsets in list files.
* Fix %include inside multi-line macros or loops.
* Fix error where NASM would generate a spurious warning on valid
optimizations of immediate values.
* Fix arguments to a number of the CVT SSE instructions.
* Fix RIP-relative offsets when the instruction carries an
immediate.
* Massive overhaul of the ELF64 backend for spec compliance.
* Fix the Geode PFRCPV and PFRSQRTV instruction.
* Fix the SSE 4.2 CRC32 instruction.
-hpa