Enable dumping huge (> 64k) pages in genesis

bvectors for a page can be smaller than the page size; zero-padding
explicitly as needed lets the build proceed further along before
failing, when configured with large GC card size.
Declare the argument type for float-radix

 Otherwise, inlined copies sometimes skip the type check.
Take bitwidth into account in BOOLEAN alien type

Some ABIs (x86/x86-64) allow garbage in unused upper bits of return
values; take that into account when converting BOOLEAN return types
to CL BOOLEANs.
Print intermediate evaluation results for some ASSERTed expressions

* The reports of errors signaled by ASSERT now print intermediate
  evaluation results under the following conditions:
   1. The ASSERTed expression is known to be a function call.
   2. Arguments in the call are not constants.

* Test the new feature in condition.impure.lisp.

* Original patch from Alexandra Barchunova; closes lp#789497.
Fix (CONCATENATE 'null ...) for generic sequences

 * (CONCATENATE 'NULL SEQUENCE1 SEQUENCE2 ...) ensures that SEQUENCE1,
   SEQUENCE2, ... are empty, but only did so for lists and
   vectors. Instead, use new function EMPTYP which works for all
   sequences. EMPTYP is not exported.

 * Add generic function SEQUENCE:EMPTYP to which EMPTYP dispatches for
   generic sequences. Methods for lists, vectors and generic sequences
   use NULL or (ZEROP (LENGTH ...)).

 * Test cases in seq.impure.lisp.

 * Patch by Jan Moringen; fixes lp#1162301.