Auto merge of #1472 - josephlr:fus, r=gnzlbg

Remove invalid Fuchsia functions

Extension of #1468

These functions are not present in Fuchsia's libc, so they cannot be
used in a program today. If Fuchsia ever decides to add these functions
to their libc, they can be added back as necessary.

These files were generated in the following manner:

1. Create a list of the current functions in Fuchsia's libc, put in `rust-functions.txt`
2. Change directory into [`fuchsia/zircon/third_party/ulib/musl/include`](https://fuchsia.googlesource.com/fuchsia/+/master/zircon/third_party/ulib/musl/include/)
3. Run a script to determine which symbols in `rust-functions.txt` are not in the include dir:
    ```bash
    for i in $(cat rust-functions.txt);
        if ! rg $i > /dev/null; then
            echo $i
        fi
    done
    ```
4. This produces [a list of 99 functions](https://github.com/rust-lang/libc/pull/1468#issuecomment-521777743), which are then removed from this crate.