Downgrade to the previous CEF release; add copyright notices

CEF 76+ switched to a new helper bundling scheme. Until I find time to
address that (looks easy -- this just isn't a high priority for me any
longer), we need to stick with versions prior to that, so downgraded
back to version 75.1.4+g4210896+chromium-75.0.3770.100.

Issue https://bitbucket.org/chromiumembedded/cef/issues/2737/macos-76-requires-multiple-helper-app
has details.

Add new files

Fix bad include of a C++ header into the C API from upstream

Update to 74.1.19+gb62bacf+chromium-74.0.3729.157

Update to CEF 74.1.19+gb62bacf+chromium-74.0.3729.157

Update to the March 31, 2019 release of CEF

Bring Windows CEF version in line with others

Update to the March 8, 2019 CEF release

Update deps

Update to CEF v3.3626.1891.g52be333 (2/15/2019)