leaning_on_rail unalias and minor fixes

BUR #24903 has been rejected.

remove alias leaning_on_rail -> against_railing
create alias leaning_on_rail -> leaning_on_railing
create implication leaning_on_railing -> railing

Related: topic #23483, topic #14422

Leaning on rail was aliased away in the first of the mentioned topics, which creates an awkward situation in cases like post #7395560. This is neither against railing, which is for characters leaning back on a railing with their butt/back, nor is it really on railing, which seems to be mainly characters standing/lying with their whole body.

Given how common this pose is (and distinct in the language, you aren't "against" something if your upper body is literally on top of it) I'd like to make a third tag, and I chose "railing" rather than "rail" to fit the other tags.

This bulk update request is pending automatic rejection in 5 days.

This bulk update request has been rejected because it was not approved within 45 days.

The bulk update request #24903 (forum #275304) has been rejected by @DanbooruBot.

John_Fantasy_XIV said:

against railing, which is for characters leaning back on a railing with their butt/back

No it's not, if you check against railing you'll find plenty of examples like post #7594910 or post #7593911. Right now it's just a generic tag for someone resting against a railing.