cmp: fix let bindings with initforms which are lists with QUOTE symbol as first element

Example:

(let ((x '(quote ...))) ...)

We really have to quote the value in all cases, si::maybe-quote would
strip away one level of quotation leaving only the equivalent
of (let ((x (quote ...))) ...) which of course is incorrect.

src/cmp/cmplet.lsp

@@ -108,7 +108,7 @@
             (multiple-value-bind (constantp value)
                 (c1form-constant-p init)
               (when constantp
-                (cmp-env-register-symbol-macro name (si::maybe-quote value))
+                (cmp-env-register-symbol-macro name `',value)
                 (setf var nil))))
           (when var
             (push var vars)

src/tests/normal-tests/compiler.lsp

@@ -2037,3 +2037,12 @@
              '((1 1 nil nil nil)
                (1 2 nil nil nil)
                (1 2 (:d 3) 3 3)))))
+
+;;; Date 2021-03-30
+;;; Description
+;;;
+;;;     let bindings of lists like '(quote ...) were miscompiled
+(test cmp.0087.let-list-containing-quote
+  (is (equal '((quote) (quote a b c))
+             (funcall
+              (compile nil '(lambda () (let ((x '(quote)) (y '(quote a b c))) (list x y))))))))