Implement case-insensitivity option

The -i/--ignore-case option allows for case-insensitive analysis by
folding all words. It's status is accessible through M_FLAG_CASEFOLD.

Add UTF-8 module with functionality for encoding, decoding and full
CaseFolding.

CaseFolding specs are implemented in src/utf_data.h but can be updated
from res/CaseFolding.txt by running parse_casefolding.pl.
Make perl-scripts executable

Add run mode to makerules.pl and parse_casefolding.pl
Add makerules file

Add makerules.mk file to the repository to allow for building without
the need to run scripts before.