Auto merge of #1996 - whitequark:patch-1, r=JohnTitor
Auto merge of #1996 - whitequark:patch-1, r=JohnTitor

Declare `seekdir` and `telldir` for Android

These declarations are the same as those for other platforms.

They are available [since API level 23](https://github.com/aosp-mirror/platform_bionic/blob/29cff99e08746f8060f32eba03df3b95acf1163d/libc/include/dirent.h#L145-L163).

rust-lang/libc,rust-lang/libc,rust-lang/libc