read-print: Add 'case' and 'cond' special forms.

* guix/read-print.scm (%special-forms): Add 'case' and 'cond'.
* tests/read-print.scm: Add tests.

guix/read-print.scm

@@ -255,6 +255,8 @@ expressions and blanks that were read."
   ;; symbol must appear within a (modify-phases ...) expression.
   (vhashq
    ('begin 1)
+   ('case 2)
+   ('cond 1)
    ('lambda 2)
    ('lambda* 2)
    ('match-lambda 1)

tests/read-print.scm

@@ -141,6 +141,21 @@ expressions."
   (let ((z (+ x y)))
     (* z z)))")
 
+(test-pretty-print "\
+(case x
+  ((1)
+   'one)
+  ((2)
+   'two))")
+
+(test-pretty-print "\
+(cond
+  ((zero? x)
+   'zero)
+  ((odd? x)
+   'odd)
+  (else #f))")
+
 (test-pretty-print "\
 #~(string-append #$coreutils \"/bin/uname\")")