LP#1509479: fix infinite loop bug in QueryParser

LP#1509479: fix infinite loop bug in QueryParser

An unclosed phrase search that has a modifier can cause QueryParser to
enter an infinite loop, tying up open-ils.storage backends.

Examples of such searches include:

  -"cats and dogs
  subject:+"physical chemistry

This patch fixes the bug by allowing the end of the query string
to terminate a phrase (in addition to a quotation mark).

To test:

[1] Verify that the t/21-QueryParser.t unit test passes
[2] To test in a *development* database, before applying the patch
    run one of the example queries.  Observe that no
    results are returned, and that one of the open-ils.storage
    drones is running at 100% CPU.
[3] Apply the patch and restart the open-ils.storage service.
[4] Try the query again; this time, it should return results
    immediately without causing an open-ils.storage drone to
    peg a CPU.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Dan Scott <dscott@laurentian.ca>