[Spec][Matrix] Define Matrix truncation in the Standard Conversion Sequences and map to Conv.vtrunc (#747)

fixes #746

Conv.vtrunc already defined the matrix trunc behavior. All that is
needed is for the Standard Conversion Sequences table to point to the
matrix trunc conversion to the right place.

Author: farzonl

specs/language/overloading.tex

@@ -301,6 +301,15 @@
 
     Vector truncation conversion & Dimensionality Reduction Conversion
           & Conversion Truncation & \ref{Conv.vtrunc} \\ \cline{1-4}
+
+    Matrix truncation (without conversion) & Dimensionality Reduction
+          & Truncation & \ref{Conv.vtrunc} \\ \cline{1-4}
+
+    Matrix truncation promotion & Dimensionality Reduction Promotion
+          & Promotion Truncation & \ref{Conv.vtrunc} \\ \cline{1-4}
+
+    Matrix truncation conversion & Dimensionality Reduction Conversion
+          & Conversion Truncation & \ref{Conv.vtrunc} \\ \cline{1-4}
     \hline
   \end{tabular}
 \end{center}