Fix build break on strict compilers

Stricter c++ compilers check template validity at point of
declaration rather than point of expansion, and complain about
a missing include file.

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>

thorlcr/shared/thor.hpp

@@ -36,6 +36,8 @@ typedef size32_t rowidx_t;
 #define RCIDXMAX ((rowidx_t)(size32_t)-1)
 #define RIPF ""
 
+#include "jexcept.hpp"
+
 // validate that type T doesn't truncate
 template <class T>
 inline rowcount_t validRC(T X)