Add user-defined envvars

apache/files/Debian/envvars-2.2.jinja

 ## If you need a higher file descriptor limit, uncomment and adjust the
 ## following line (default is 8192):
 #APACHE_ULIMIT_MAX_FILES='ulimit -n 65536'
+
+{%- for envvar in salt['pillar.get']('apache:envvars', []) %}
+{{ envvar }}
+{%- endfor %}

apache/files/Debian/envvars-2.4.jinja

 ## This will produce a verbose output on package installations of web server modules and web application
 ## installations which interact with Apache
 #export APACHE2_MAINTSCRIPT_DEBUG=1
+
+{%- for envvar in salt['pillar.get']('apache:envvars', []) %}
+{{ envvar }}
+{%- endfor %}