update license of compat and crypto

- change license to be just MIT for all files in compat and crypto
- also add missing header end comments
- ensure default header include style
cleanup license and header end comment in chain.cpp/.h
Fix vector out of bounds in script tests
Merge pull request #5003

68af7d0 Fix vector out of bounds in script tests (Pieter Wuille)
Merge pull request #4990

7bec6dd cleanup license and header end comment in chain.cpp/.h (Philip Kaufmann)
0db65d8 update license of compat and crypto (Philip Kaufmann)
Abstract out SignatureChecker
Make signature cache optional
Replace SCRIPT_VERIFY_NOCACHE by flag directly to checker