shell: some additions to *sh-misc/* tests

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

shell/hush_test/hush-misc/env_and_func.tests

@@ -1,4 +1,8 @@
 var=old
 f() { echo "var=$var"; }
+# bash: POSIXLY_CORRECT behavior is to "leak" new variable values
+# out of function invocations (similar to "special builtins" behavior);
+# but in "bash mode", they don't leak.
+# hush does not "leak" values. ash does.
 var=val f
 echo "var=$var"