relay: fix number of bytes sent/received on 32-bit systems
trigger: fix hook count on 32-bit systems
api: fix function string_decode_base64

The result of function was sometimes wrong, for example base64 decoding of
"YWJj" was returning "ab" instead of "abc".
core: fix result of hash function (in hashtables) on 32-bit systems
tests: add tests of base 16/64 decoding/encoding
tests: add tests of functions string_is_command_char and string_input_for_buffer