Mark all exception types as CoreExport.

From the GCC docs:

>Exception catching of a user defined type in a binary other than
>the one which threw the exception requires a typeinfo lookup.

Closes #335.

include/modules/sql.h

@@ -81,7 +81,7 @@ namespace SQL
 
 	/** A SQL exception, can be thrown at various points
 	 */
-	class Exception : public ModuleException
+	class CoreExport Exception : public ModuleException
 	{
 	public:
 		Exception(const Anope::string &reason) : ModuleException(reason) { }