Colon : in custom field search causes searching of wrong field

Steps to reproduce:
1) Perform a new search on http://jira.atlassian.com/secure/IssueNavigator.jspa?mode=show&createNew=true
2) Under project, select "A Test Project"
3) Click the "Click here to refresh the search menu" link.
4) In the Custom Fields section, find the "Random text" field and enter the following parameter: priority:1
5) Click the "View >>" button to perform the search.

Expected results:
Search result contains bugs where the "Random text" field contains the word "priority" or the number "1"

Actual results:
We just searched on the Priority field! Search result contains priority 1 bugs.

A more common scenario is a user searching for a URL. They enter http://www.example.com/ into a custom field searcher but get no matches because JIRA is now attempting to search a field called "http".

This bug was fixed for the Summary/Description/Comments/Environment text searcher (which uses MultipleFieldSingleValueLuceneParameter) in JRA-5394. But this fix does not work for custom text fields (which use SingleFieldSingleValueLuceneParameter).