Add nightly build

Update actions to latest versions

Add point about commenting

Make formatting fixes a downloadable artifact

Don't stop after the first check

Output error messages to the github summary file

Fix crash introduced by commit 447e579062c7692

clang-format

Add missing #define constant for null key

clang-format

Use a different struct type for key types

Fix cases where *Key and *Value types were confused

Add check that value types can be redefined

Add header to test value types can be redefined

Add SortedArrayValue NULL constant