Fix copyright
See:
https://github.com/Mind4SE/mind-compiler/commit/4b4658364bf9542a0202ba7d49369b501248b082#adl-backend-src-test-java-org-ow2-mind-testmissingmethodserror-java-P2
Fix test implem
See:
https://github.com/Mind4SE/mind-compiler/commit/4b4658364bf9542a0202ba7d49369b501248b082#adl-backend-src-test-java-org-ow2-mind-testmissingmethodserror-java-P80
Fix test implem comment to match real code
See:
https://github.com/Mind4SE/mind-compiler/commit/4b4658364bf9542a0202ba7d49369b501248b082#adl-backend-src-test-resources-functional-missingmeth-helloworldsplitimpl-server2-c-P13
Removed unused error + changed error numbers accordingly