Fix gh-1166 ESP failing to load xml processor

The extern "C" was accidentally removed from the prototypes for the
functions that esp dynamically loads from xslt processing  library. This
left ESP unable to do any xslt processing.

Signed-off-by: Anthony Fishbeck <Anthony.Fishbeck@lexisnexis.com>

system/xmllib/xmlvalidator.hpp

@@ -49,7 +49,7 @@ interface XMLLIB_API IXmlDomParser : public IInterface
 };
 
 
-XMLLIB_API IXmlDomParser* getXmlDomParser();
+extern "C" XMLLIB_API IXmlDomParser* getXmlDomParser();
 
 
 #endif

system/xmllib/xslprocessor.hpp

@@ -125,6 +125,6 @@ interface XMLLIB_API IXslProcessor : public IInterface
     virtual int getCacheTimeout() = 0;
 };
 
-XMLLIB_API IXslProcessor* getXslProcessor();
+extern "C" XMLLIB_API IXslProcessor* getXslProcessor();
 
 #endif