Rebind *HANDLER-CLUSTERS* in SIGNAL to prevent infinite recursion

Commit

  3f3407f0 "Fewer *HANDLER-CLUSTERS* special re-bindings in SIGNAL"

removed some of the re-bindings of *HANDLER-CLUSTERS* in SIGNAL as an
optimization. This lead to the current cluster not being removed
from *HANDLER-CLUSTERS* when testing condition types which in turn lead
to infinite recursive SIGNAL calls when a condition type test signaled
an error.

Re-bind *HANDLER-CLUSTERS* to not contain the current cluster before
applying condition type tests.

fixes lp#1378939
Speed up SIGNAL via dx type check functions in %HANDLER-BIND

This avoids the type specifier parsing and out-of-line TYPEP overhead of
the previous implementation which stored type specifiers
in *HANDLER-CLUSTERS*.

Another benefit are compile-time warnings about undefined condition
types in %HANDLER-BIND clauses.

Unfortunately, %HANDLER-BIND expands to less compact code.
Add SET-MACRO-POLICY as mentioned on sbcl-devel

Not documented as an extension yet - still in a an immature state.