Previously this used unofficial, apple specific syntax (with fallback
macros for gnu binutils), since Xcode 5.x didn't support the official
syntax of these instructions. Since Xcode 6 has been out for quite a
number of months already, it should be safe to require this (for
building 64 bit binaries for iOS, armv7 builds can still be built
with older Xcode versions).
This clarifies the code by avoiding apple specific syntax in the
assembler instructions.
Since Xcode 5.1, the apple tools actually support using the
official, correct syntax for the ext instructions. This syntax
is already used in a number of places already - use it consistently,
and get rid of the compatibility hacks.
This fixes building with gnu binutils, which don't support this
nonstandard form of the instructions.
Once Apple's tools support the proper standard form of the
instructions, the code should be updated to use that everywhere
instead, and these macros should be removed.
