x86: re-work ISA extension dependency handling

x86: re-work ISA extension dependency handling

Getting both forward and reverse ISA dependencies right / consistent has
been a permanent source of mistakes. Reduce what needs specifying
manually to just the direct forward dependencies. Transitive forward
dependencies as well as reverse ones are now derived and hence cannot go
out of sync anymore (at least in the vast majority of cases; there are a
few special cases to still take care of manually). In the course of this
several CPU_ANY_*_FLAGS disappear, requiring adjustment to the
assembler's cpu_arch[].

Note that to retain the correct reverse dependency of AVX512F wrt
AVX512-VP2INTERSECT, the latter has the previously missing AVX512F
prereq added.

Note further that to avoid adding the following undue prereqs:
* ATHLON, K8, and AMDFAM10 gain CMOV and FXSR,
* IAMCU gains 387,
auxiliary table entries (including a colon-separated modifier) are
introduced in addition to the ones representing from converting the old
table.

To maintain forward-only dependencies between AVX (XOP) and SSE* (SSE4a)
(i.e. "nosse" not disabling AVX), reverse dependency tracking is
artifically suppressed.

As a side effect disabling of SSE or SSE2 will now also disable AES,
PCLMUL, and SHA (respective elements were missing from
CPU_ANY_SSE2_FLAGS).