Docu update.

doc/tex/environment.tex

@@ -11,6 +11,7 @@ The following table describes the environment variables that affect {\CDI}.
 %\cellcolor{pcolor2}
 {\bfseries Variable name}           &  {\bfseries Default} & {\bfseries Description} \\ \hline
 CDI\_CONVERT\_CUBESPHERE &        1   & Convert cubed-sphere data to unstructured grid. \\
+CDI\_CHUNK\_CACHE            &         0   & Set the NetCDF4 chunk cache size. \\
 CDI\_GRIB1\_TEMPLATE          &   None   &  Path to a GRIB1 template file for GRIB\_API. \\
 CDI\_GRIB2\_TEMPLATE          &   None   &  Path to a GRIB2 template file for GRIB\_API. \\
 CDI\_INVENTORY\_MODE        &   None   &  Set to time to skip double variable entries. \\