* doc/ref/vm.texi: Document new instruction.
* libguile/vm-i-system.c: Add it to the VM.
* module/language/assembly.scm: Compile (const %nil) to (make-nil) assembly.
* module/language/glil/decompile-assembly.scm: Handle (make-nil)
* module/language/elisp/compile-tree-il.scm: Use (const %nil) for nil.
* module/language/elisp/README: New file containing some notes.
* module/language/elisp/compile-tree-il.scm: New file with compilation code.
* module/language/elisp/spec.scm: Updated language definition.
* module/system/base/syntax.scm (keywords): Don't enable :keywords, it
breaks code that may assume that ':foo is a symbol, like boot-9.
* module/*.scm: Don't use :keywords, use #:keywords. The user can decide
if she wants #:keywords in their .guile, and :keywords might make us
compile modules differently.
