Provide an alternate mechanism for constant wrapping

  -  allow to opt out from interning constants: :INTERN-CONSTANTS
  -  allow to access constants via dedicated accessor: :CONSTANT-ACCESSOR
constant accessor: fix the generated compiler macro
constant accessor: more idiomatic loops
constant interning exclusion: don't be so all-or-nothing
fix non-SBCL case: excluded-p is not defined
exclusion set specifiers: cache compiled expression scanners
c-include: fix the stray EXCLUDED-P that slipped somehow..
Merge pull request #8 from deepfire/master

Provide an alternate mechanism for constant wrapping