PURE_REWRITE_CONV : (thm list -> conv)
Rewrites a term with only the given list of rewrites.
This conversion provides a method for rewriting a term with the theorems given,
and excluding simplification with tautologies in implicit_rewrites. Matching
subterms are found recursively, until no more matches are found.
For more details on rewriting see
PURE_REWRITE_CONV is useful when the simplifications that arise by
rewriting a theorem with implicit_rewrites are not wanted.
Does not fail. May result in divergence, in which case
PURE_ONCE_REWRITE_CONV can be used.