Add Doxygen 1.9.1 binaries

[neofelis2X]

Hi @swt2c,

to make the build process of the wxPython docs as smooth as possible I propose to add Doxygen version 1.9.1. This specific version is expected by wxWidgets/docs/doxygen/regen.sh which is called during the build process.

This also removes one warning message from the build process and 1.9.1 is a bit less ancient than 1.8.8

All files are directly from here: https://github.com/doxygen/doxygen/releases/tag/Release_1_9_1

• doxygen-1.9.1.windows.x64.bin.zip
• Doxygen-1.9.1.dmg (extracted)
• doxygen-1.9.1.linux.bin.tar.gz

I tested the windows and the macOS variant and they run without problems.
The windows binary is packed as a tar.bz2 because it also includes the libclang.dll
I don't know if you even accept binaries in a PR, but I added the hashes so you can check the files:

win

Name: doxygen-1.9.1-win32.exe

Size: 18841600 Bytes : 17 MiB

MD5: 90439896025dc8ddcd5d767ab2c2c489

SHA256: 3ef1084566b8c9bf33706d47b974ad07ddb4d2e26037eb199ff406c62f4c693e

Name: libclang.dll

Size: 44775936 Bytes : 42 MiB

MD5: 01993315cc63ab5c37137d79be3ac46b

SHA256: 178bf40c7531781431456466234ed5ac7f1171a58bb696645849572a41e8b640

linux

Name: doxygen-1.9.1-linux

Size: 22112160 Bytes : 21 MiB

MD5: 5e869ab2085183f3d297b0156a10d4a1

SHA256: 2712aee1f6801eaec528770962cfe83d3ab68059a42a1f634ce918efcacac793

macos

Name: doxygen-1.9.1-darwin

Size: 189404544 Bytes : 180 MiB

MD5: 6912d41cef5971fb07573190849a8a84

SHA256: 01bc02017b83369a75d9f52c687217395c772382ee5e9157d0afbc2e2929ce5e

Since the version number and hashes are hardcoded into Phoenix build.py I will then update it for wxWidgets/Phoenix#2672

[swt2c]

Thanks, I squashed your commits and merged manually.