* .dir-locals.el: Add with-fresh-name-state.
* module/language/cps.scm (fresh-label, fresh-var): Signal an error if
the counters are not initialized.
(with-fresh-name-state): New macro.
(make-cont-folder): New macro, generates an n-ary folder.
(compute-max-label-and-var): New function, uses make-cont-folder.
(fold-conts): Use make-cont-folder.
(let-gensyms): Remove.
* module/language/cps/arities.scm:
* module/language/cps/closure-conversion.scm:
* module/language/cps/constructors.scm:
* module/language/cps/dce.scm:
* module/language/cps/elide-values.scm:
* module/language/cps/reify-primitives.scm:
* module/language/cps/specialize-primcalls.scm: Use let-fresh instead of
let-gensyms, and wrap in a with-fresh-name-state as needed.
* module/language/tree-il/compile-cps.scm: Remove hack to avoid
importing let-gensyms from (language tree-il).
* module/language/cps.scm ($callk): New expression type, for calls to
known labels. Part of "low CPS".
* module/language/cps/arities.scm:
* module/language/cps/closure-conversion.scm:
* module/language/cps/compile-bytecode.scm:
* module/language/cps/dce.scm:
* module/language/cps/dfg.scm:
* module/language/cps/effects-analysis.scm:
* module/language/cps/simplify.scm:
* module/language/cps/slot-allocation.scm:
* module/language/cps/verify.scm: Adapt call sites.
* libguile/vm-engine.c (call-label, tail-call-label): New instructions.
Renumber the rest; this is an ABI change.
* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION):
* module/system/vm/assembler.scm (*bytecode-minor-version*): Bump.
* doc/ref/compiler.texi (CPS in Guile): Document $callk.
