Enhance VMS exporting make environment variables.

* config.h-vms.template: add feature macro USE_DCL_COM_FILE to always
write a DCL command file, enabled by default.
* vmsjobs.c: with USE_DCL_COM_FILE enabled write make variables as DCL
symbol assignments into the command file.  This enables printing
directory and make level info for recursive use of make. This also
enables forced DCL symbol substitution in the actions.
2 files changed