[xslt] Re-use of parsed stylesheet

["William M. Brack" <wbrack mmm com hk>]

We have discovered two problems with calling xsltParseStylesheetFile,
followed by multiple calls of xsltApplyStylesheet (using different
documents):-

1) For all user parameters presented to xsltApplyStylesheet, the variables
are added to the global stylesheet variable list (xsltRegisterGlobalVariable
called by xsltEvalUserParams) but never removed.

2) Compiled XPath expressions (which are related to the document being
processed) are retained in the stored variable information. After the first
document has been processed and released, this causes a crash.

A proposed patch (against libxslt-0.9.0) is attached.

Bill Brack
ABC QuickSilver