Removes ndk-glue + ndk-macro as part of rust-mobile#372 modularization

The ndk-glue and ndk-macro subdirectores have been split into a
stand-alone repository at: https://github.com/rust-mobile/ndk-glue

This is being done as part of the modularization effort described in
issue rust-mobile#372

The stand-alone repository was filtered like this:

```
git clone https://github.com/newren/git-filter-repo
git clone https://github.com/rust-windowing/android-ndk-rs.git ndk-glue
cd ndk-glue
py ../git-filter-repo/git-filter-repo \
    --path ndk-glue --path ndk-macro \
    --path ndk-examples --path-rename ndk-examples:examples \
    --path LICENSE-APACHE --path LICENSE-MIT \
    --path Cargo.toml --path rustfmt.toml \
    --path .github --path .gitignore
```

The last commit in this repo that is included within the
stand-alone repository is 107f03e

Although ndk-glue is also being deprecated at the same time as
splitting it out this commit doesn't make any README changes for
this repo yet which will be addressed separately.

Cargo.toml

@@ -2,10 +2,8 @@
 members = [
     "ndk",
     "ndk-context",
-    "ndk-macro",
     "ndk-build",
     "ndk-examples",
-    "ndk-glue",
     "ndk-sys",
     "cargo-apk",
 ]