cgi-io: update to version 2020-10-27

cgi-io: update to version 2020-10-27

Contains following list of changes:

 ab4c3471b261 tests: add cram based unit tests
 7b4e3241e1bd tests: add cgi-io built with clang sanitizers
 21831f45d16d Disable session ACLs during unit testing
 2f525417b5df Add initial GitLab CI support
 57f1c4f18cb6 Add .gitignore
 09f9ac5066ee Fix off-by-one in postdecode_fields
 ed8ce0d5d28b Add fuzzing of utility functions
 a61581819800 Add fuzzing of multipart_parser
 6b0615b728ed Refactor utility functions into static library
 a0ed2c9a7a72 Fix clang compiler errors
 232659da19a4 Fix possible NULL dereference
 8e5719b37a67 Fix warnings reported by clang-10 static analyzer
 b99aa8a64cca Remove Makefile

Signed-off-by: Petr Štetiar <ynezz@true.cz>