x86/Solaris: support Sun form of CMOVcc

Sun specifies an alternative form for CMOVcc [1], which for some reason
we never cared to support, even if - as per gcc's configure checking for
it - it may have been the only permitted form at some point.

While documentation doesn't indicate FCMOVcc to have similar alternative
forms, gcc assumes so. Hence cover FCMOVcc as well.

[1] https://docs.oracle.com/cd/E37838_01/html/E61064/ennbz.html#XALRMeoizm