[llvm] [STLExtras] Introduce bind_{front, back}, [not_]equal_to (PR #175056)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

I've implemented a modified version of Yanzuo's suggestion, with a note about perfect-forwarding and this. I hope this is okay?

Ref: https://eel.is/c++draft/expr.prim.lambda#17
Ref: https://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#2011
Ref: https://stackoverflow.com/q/55559308/1088790
Ref: https://vittorioromeo.info/index/blog/capturing_perfectly_forwarded_objects_in_lambdas.html

https://github.com/llvm/llvm-project/pull/175056