By default, windows.h exposes a large number of problematic define statements
which are UpperCamelCase, such as a define from `CreateWindow` to
`CreateWindow{A,W}`.

As many of these names are generic (e.g. CreateFile, CreateWindow), they can
mess up Gecko code that may legitimately have its own methods with the same
names.

The header also defines some traditional SCREAMING_SNAKE_CASE defines which
can mess up our code by conflicting with local values.

This patch adds a simple code generator which generates wrappers for these
defines, and uses them to wrap the windows.h wrapper using the `stl_wrappers`
mechanism, allowing us to use windows.h in more places.

Differential Revision: https://phabricator.services.mozilla.com/D10932