Tiny bugfix for printing symbols in ldb.

Those unlucky enough to crash into ldb might have thought it
another bug to see "plist: #<ptr to simple vector>"
Fix SB-INTROSPECT contrib module's structure inquiry functions.
Fix structure accessor location retrieval.

Now that structure functions are made with DEFUN, there's nothing
special required to retrieve their location, the code which performed
the tricks can be removed.
Disable failing tests of lockfree concurrent hashtable on ppc.
compiler/sparc/float: Fix mis-compilation of signed-to-float conversion.

  * Found with the able assistance of Paul Khuong, a number stack
reference was being made using the TN-OFFSET from a register TN,
occasionally working correctly by sheer happenstance.

  * And this, at long last, fixes the build on SPARC, broken since
the PACK changes a couple of months ago.
Fix floating point conversion on PPC.

%single/double-float VOPs multiplied the stack offset by 4 twice,
overwriting the wrong stack location.
1.1.17: will be tagged as "sbcl-1.1.17"