Dovecot core doesn't have copyright notices in header files.

Patch by Andreas Schulze.

perl -i -pe 's/unsigned int ([^,:;]+):1;/bool $1:1;/' **/*.[ch]

- Changed operand read functions to prove exec status return codes in stead of boolean.
- Restructured optional-operand, stringlist and string-match APIs to provide execution status (error code) upon failure.
- Corruption errors are only produced when the binary is actually corrupt. Normal failures should never cause a recompile attempt anymore.
- Simplified optional-operand API.
- Cleaned up test command implementations that use the string-match API.

Resolved code duplication among commands that use comparators and match-types and found problems in the imapflags extension in the process.

Significantly improved handling of old/corrupt binaries and revised matching implementation in the process.