SQL Portability Patches

First set of patches to assist RDBMS portability as previously discussed on the general development list. This covers the following:

 - Identifier quoting of SQL reserved words:
   * LANGUAGE
   * MODULE
   * OPTION
   * TIME
   * LEVEL
   * POSITION

 - Identifier quoting of Virtuoso (and Oracle) reserved word:
   * PASSWORD

 - Quoting of string literals in some places

 - Correct use of non-standard != logic comparison operator to <>

 - Casting of some long types used in SQL functions that may not support long types

 - Fixed conditional join to categories in weblinks model (mod_weblinks seems to assume the categories table (aliased "c") is always present)

 - Fixed duplication of column list in mod_articles_news helper

These changes are organised by front/admin then by component/module/plugin but squashed into single commits with respect to the categories of changes listed above. Given that none of the categories of changes are intended to alter any functional features, I hope that this is suitably divided and correct granularity for manual testing.

If preferred the commits are available unsquashed on separate branches under wdaniels/joomla-cms as indicated by the [branch-name] prefixes of the squashed commits messages where merged into this (sql92) branch.

These patches are relatively trivial and I do not believe to be contentious. Further patch sets I intend to raise for discussion on joomla platform/cms lists as appropriate.

NB: There remains RDBMS portability issues with the use of MySQL DATE_FORMAT function in mod_relateditems and mod_weblinks which require some further investigation. Also issues remain with quoting for the LIKE conditions in mod_relateditems. No doubt other issues also remain; this patch set is not intended to be exhaustive, even with respect to the identified issues.

[JoomlaCode #28391]