BUILD: check for sys/eventfd.h
RCORE: platform.cc: use x86 asm instructions on x86 only
RCORE: start moving assembler macros into cpuasm.hh
RCORE: add missing __amd64__ to rdtsc macro
RCORE: only use lfence/sfence on 64bit x86, else fallback to __sync_synchronize
RCORE: math.cc: move asm rounding mode check here
UI: remove unused include
RCORE: Aida: expose EventFd, fallback to pipe2 if eventfd is not available
RCORE: loop: use Aida::EventFd
RCORE: printf fix for 32bit
RCORE: aida: assertion fix for 32bit
AIDA: constrain to maximum signed enum range on 32bit platforms: +-9223372036854775807
Merge branch 'portability'

* portability:
  AIDA: constrain to maximum signed enum range on 32bit platforms: +-9223372036854775807
  RCORE: aida: assertion fix for 32bit
  RCORE: printf fix for 32bit
  RCORE: loop: use Aida::EventFd
  RCORE: Aida: expose EventFd, fallback to pipe2 if eventfd is not available
  UI: remove unused include
  RCORE: math.cc: move asm rounding mode check here
  RCORE: only use lfence/sfence on 64bit x86, else fallback to __sync_synchronize
  RCORE: add missing __amd64__ to rdtsc macro
  RCORE: start moving assembler macros into cpuasm.hh
  RCORE: platform.cc: use x86 asm instructions on x86 only
  BUILD: check for sys/eventfd.h