Identify requirements text in the SQLITE_CONFIG_ documentation. Fix a typo

(a duplicated word) in part of that documentation.  Add some requirements
marks for DETACH to the test scripts.  No code changes.

FossilOrigin-Name: 1be0a3adaba2914c65c46fbebc4906ae4e70f899

test/attach2.test

@@ -377,6 +377,9 @@ do_test attach2-6.2 {
   }
 } {1 {cannot ATTACH database within transaction}}
 
+# EVIDENCE-OF: R-59740-55581 This statement will fail if SQLite is in
+# the middle of a transaction.
+#
 do_test attach2-6.3 {
   catchsql {
     DETACH aux;