Fixed 0008421: Recently visted is showing some serialized filter instead of bug ids.

• The cause of the bug was that the token_update() didn't have a WHERE clause, hence, updating one token will update all the tokens in the table. Hence, "last visited" token got overwritten by the value of a filter token.

• Did some misc. cleanup in token_api.

git-svn-id: http://mantisbt.svn.sourceforge.net/svnroot/mantisbt/trunk@4611 <a class="text" href="/?p=mantisbt.git;a=object;h=f5dc347c">f5dc347c</a>-c33d-0410-90a0-b07cc1902cb9