Fix a situation where a pointer which should point to dynamically

Fix a situation where a pointer which should point to dynamically
allocated memory was instead pointed to a static string.  A later
free() on the value of the pointer was a possible source of reported
"warning: pointer to wrong page" messages from cron.

Use consistent types in sizeof when malloc'ing memory for the
environment.

PR:		kern/12248, bin/11169, bin/9722