numerous issues fixed:
* buffer overflows
* error conditions aren't checked (crash if file doesn't exist)
* accessing random unallocated memory
* hard-coded password
* arbitrary hard-coded key id limit
* incomprehensible error messages (for key_id == 0 it reported
  "The key could not be initialized", for syntax errors the message was
  "Wrong match of the keyID, see the template", for a key id
  larger than hard-coded limit the message was "No asked key", and there
  was an error "Is comment" for a comment).
* tons of small mallocs, many are freed few lines down in the code
* malloc(N) and new char[N] are used both, even in the same function
* redundant memory copies
* pcre - "I can solve it with regular expressions" - with incorrect regexes
* parser context stored in a singleton
* keys are stored as strings and are strlen-ed and hex2bin-ed on every
  get_key() request
* lots of useless code (e.g. sprintf instead of a pointer assignment,
  checking of the file length to read a part of it in a fixed buffer,
  multiplying by sizeof(char) in many places, etc)
* this list is not exhaustive