MFH: r413035

• update to 2.4.20
• use ${OPTION}_IMPLIES and remove some IGNORES
• turn on proxy_html and xml2enc as default [1]

[1] Often requested by users. The modules are not enabled in

the default configuration.

Full changelog for apache version 2.4.19/2.4.20:
http://www.apache.org/dist/httpd/CHANGES_2.4.20

Note: Apache httpd 2.4.19 was not released.

Approved by: ports-secteam (junovitch)