Since commit 5b9da05b7a (Windows: Embed version information into CMake
binaries, 2017-10-25, v3.11.0-rc1~411^2) our binaries have version
information that prevents a `.msi` downgrade from replacing them by
default. Configure the re-install mode:
* a: reinstall all files regardless of version
* m: rewrite all per-machine registry entries
* u: rewrite all per-user registry entries
* s: reinstall shortcuts and icons
Fixes: #19006
Run the `Utilities/Scripts/clang-format.bash` script to update
all our C++ code to a new style defined by `.clang-format`.
Use `clang-format` version 3.8.
* If you reached this commit for a line in `git blame`, re-run the blame
operation starting at the parent of this commit to see older history
for the content.
* See the parent commit for instructions to rebase a change across this
style transition commit.
In `detect_nsis_overwrite.cpp` we include windows.h first, and we must
preserve that. Place the include in an isolated block so that tools
that sort includes do not move it.
Use a custom action to look for Uninstall.exe in the user
selected installation prefix.
Its presence indicates a previous NSIS installation.
Inform the user and request manual resolution of the issue.
