Bug 1316990 - part 2b - add initial set of approved licenses for Rust packages; r=gerv

This commit adds the initial whitelist of (mostly) SPDX license
identifiers and the initial whitelist of separately-specified license
files for those packages that require it.  For gamma-lut, the license
that the hash identifies is:

https://hg.mozilla.org/mozilla-central/file/47611a305c44/third_party/rust/gamma-lut/LICENSE

For deque, the license that the hash identifies is:

https://hg.mozilla.org/mozilla-central/file/47611a305c44/third_party/rust/deque/LICENSE-MIT

Integrating any new licenses into about:license is left as separate work
for the time being.

python/mozbuild/mozbuild/vendor_rust.py

@@ -136,6 +136,20 @@ Please commit or stash these changes before vendoring, or re-run with `--ignore-
         # solely by a build peer; any additions must be checked by somebody
         # competent to review licensing minutiae.
         LICENSE_WHITELIST = [
+            'Apache-2.0',
+            'Apache-2.0 / MIT',
+            'Apache-2.0/MIT',
+            'Apache-2 / MIT',
+            'BSD-3-Clause', # bindgen (only used at build time)
+            'CC0-1.0',
+            'ISC',
+            'ISC/Apache-2.0',
+            'MIT',
+            'MIT / Apache-2.0',
+            'MIT/Apache-2.0',
+            'MIT OR Apache-2.0',
+            'MPL-2.0',
+            'Unlicense/MIT',
         ]
 
         # This whitelist should only be used for packages that use a
@@ -147,6 +161,10 @@ Please commit or stash these changes before vendoring, or re-run with `--ignore-
         # reviewed solely by a build peer; any additions must be checked by
         # somebody competent to review licensing minutiae.
         LICENSE_FILE_PACKAGE_WHITELIST = {
+            # Google BSD-like license; some directories have separate licenses
+            'gamma-lut': '1f04103e3a61b91343b3f9d2ed2cc8543062917e2cc7d52a739ffe6429ccaf61',
+            # MIT
+            'deque': '6485b8ed310d3f0340bf1ad1f47645069ce4069dcc6bb46c7d5c6faf41de1fdb',
         }
 
         LICENSE_LINE_RE = re.compile(r'\s*license\s*=\s*"([^"]+)"')