Resolves #2070 Add new x-remote-addr var to the get_ip() function

[effone]

Attempt to resolve #2070

Task List:

• Modify get_ip( ) function to handle various headers
• Use PHP filters (and flags) to validate IP in place of REGEX
• Cover CloudFlare IP override
• Add ACP Setting for users to select desired headers

@dvz @euantorano (or some expert/s) please review the ordering in $filter_headers array. This is important as the first match will be considered to return.

[effone]

The ACP settings will be created after review / confirmation for considered headers and their check sequence.

[dvz]

A setting should be used as the first and only source for IP addresses, perhaps with a fallback to $_SERVER['REMOTE_ADDR']. The value in chosen header could be validated when settings are saved.

The actual list for attempts could be included in the installation process - see https://community.mybb.com/thread-219338.html

[skmedix]

Remove space from the end of the string

Suggested change

	'HTTP_CF_CONNECTING_IP ', // Cloudflare Proxy
	'HTTP_CF_CONNECTING_IP', // Cloudflare Proxy

[Eldenroot]

@effone - will you finish this one? Thx

[effone]

Yes @Eldenroot , need to rewrite the PR, cause the approach outlined by @dvz is different from what it is now.

[Ben-MyBB]

@effone Ping! Reminder about this PR :)

[effone]

The actual list for attempts could be included in the installation process

Failed to understand this part @dvz

[dvz]

Fixed the link (https://community.mybb.com/thread-219338.html) - when the installer is rewritten, the header name can be detected automatically.