xsltAddTextString: Check for overflow when merging text nodes.

third_party/libxslt/libxslt/xsltInternals.h

 /*
  * Summary: internal data structures, constants and functions
  * Description: Internal data structures, constants and functions used
  *              by the XSLT engine.
  *              They are not part of the API or ABI, i.e. they can change
  *              without prior notice, use carefully.
  *
  * Copy: See Copyright for the status of this software.
  *
  * Author: Daniel Veillard
@@ skipping 1736 matching lines @@
      * (XSLT 1.0 term: "Result Tree Fragment")
      */
     xmlDocPtr       tmpRVT;             /* list of RVT without persistance */
     xmlDocPtr       persistRVT;         /* list of persistant RVTs */
     int             ctxtflags;          /* context processing flags */
 
     /*
      * Speed optimization when coalescing text nodes
      */
     const xmlChar  *lasttext;           /* last text node content */
-    unsigned int    lasttsize;          /* last text node size */
-    unsigned int    lasttuse;           /* last text node use */
+    int             lasttsize;          /* last text node size */
+    int             lasttuse;           /* last text node use */
     /*
      * Per Context Debugging
      */
     int debugStatus;                    /* the context level debug status */
     unsigned long* traceCode;           /* pointer to the variable holding the mask */
 
     int parserOptions;                  /* parser options xmlParserOption */
 
     /*
      * dictionary: shared between stylesheet, context and documents.
@@ skipping 199 matching lines @@
                                                  xsltDocumentPtr doc,
                                                  xsltKeyDefPtr keyd);
 XSLTPUBFUN int XSLTCALL
                         xsltInitAllDocKeys      (xsltTransformContextPtr ctxt);
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* __XML_XSLT_H__ */