docs: Modernize install.xml

docs: Modernize install.xml

- Remove mirrors reference and binary releases (both retired)
- Update all external links to https
- Update version examples to current 2.4.66/2.4.67
- Replace two-step gzip/tar with single tar xzf
- Reword download section for source builds
- Consolidate verification link to verification.html
- Remove minimizing language (easy, simple, simply)
- Add language="sh" to all highlight blocks
- Update disk space: 200 MB build (was 50), 50 MB installed (was 10)
- Replace deprecated ntpdate/xntpd with systemd-timesyncd/chrony
- Remove outdated Perl 5.003 version floor
- Update release examples from dead 2.0/2.2 to 2.4/2.6
- Update 'Mac OS X, Solaris' to 'macOS'
- Requirements intro: 'building' → 'building and running'

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1934638 13f79535-47bb-0310-9956-ffa450edef68