emacs: Use whitelist instead of blacklist for term escaping

Previously, the term escaper used a blacklist of characters that
needed escaping.  This blacklist turned out to be somewhat incomplete;
for example, it did not contain non-whitespace ASCII control
characters or Unicode "fancy quotes", both of which do require the
term to be escaped.

Switch to a whitelist of characters that are definitely safe to leave
unquoted.  This fixes the broken test introduced by the previous
patch.

emacs/notmuch-lib.el

@@ -426,7 +426,10 @@ user-friendly queries."
 
   (save-match-data
     (if (or (equal term "")
-	    (string-match "[ ()]\\|^\"" term))
+	    ;; To be pessimistic, only pass through terms composed
+	    ;; entirely of ASCII printing characters other than ", (,
+	    ;; and ).
+	    (string-match "[^!#-'*-~]" term))
 	;; Requires escaping
 	(concat "\"" (replace-regexp-in-string "\"" "\"\"" term t t) "\"")
       term)))

test/T310-emacs.sh

@@ -954,7 +954,6 @@ output=$(notmuch search --output=messages 'tag:search-global-race-tag')
 test_expect_equal "$output" "id:$gen_msg_id_1"
 
 test_begin_subtest "Term escaping"
-test_subtest_known_broken
 output=$(test_emacs "(mapcar 'notmuch-escape-boolean-term (list
 	\"\"
 	\"abc\`~\!@#\$%^&*-=_+123\"