(pcase--dontcare-upats): New var.
(pcase-let, pcase-let*): Generate better code.
Accept the same bodies as `let'.
(pcase-dolist): New macro.
(pcase--trivial-upat-p): New helper function.
(pcase--expand): Strip leading "(let nil" if any.
(pcase-if): Add one minor optimization.
(pcase-split-equal): Rename from pcase-split-eq.
(pcase-split-member): Rename from pcase-split-memq.
(pcase-u1): Add strings to the member optimization.
Add `guard' variant of predicates.
(pcase-q1): Add string patterns.
