Does not build - emit-skip issue about stmx

[cosmos72]

Found.
It's an internal change in sbcl, which confuses stmx detection of x86-64 instructions 'xbegin' 'xend' ... that were added to sbcl 1.3.4 (previously, these instructions were defined by stmx itself).

Such detection code is obviously examining sbcl internals in unsupported ways, and infact it keeps breaking (it already happened with sbcl 1.4.10, as you reported in issue #14)

I guess it must be rewritten as "assume that sbcl >= 1.3.4 defines 'xbegin' 'xend'... and assume that sbcl < 1.3.4 does not define them".

Or, more brutally, drop support for sbcl < 1.3.4 - although I'd rather preserve it, as I have no idea whether it's still actively used.

[cosmos72]

Fixed,
both in master branch (commit f8de8cc)
and in stable branch pulled by quicklisp (commit bf11fcd)

The solution I applied is "assume that sbcl >= 1.3.4 defines 'xbegin' 'xend'... and assume that sbcl < 1.3.4 does not define them" instead of inspecting SBCL internals