lib: add "verbose" versions of notmuch_database_{open,create}

lib: add "verbose" versions of notmuch_database_{open,create}

The compatibility wrapper ensures that clients calling
notmuch_database_open will receive consistent output for now.

The changes to notmuch-{new,search} and test/symbol-test are just to
make the test suite pass.

The use of IGNORE_RESULT is justified by two things. 1) I don't know
what else to do.  2) asprintf guarantees the output string is NULL if
an error occurs, so at least we are not passing garbage back.