Updated return values of some atcommands.
Altered many function types from int to bool(C99) and added meaningful return values.
Altered many function types from int to void as they didn't have any meaningful return value.
Replaced chrif_char_offline with a macro as this function did exactly the same as chrif_char_offline_nsd.
Reverted some minor mistakes in chrif_parse, char_ask_name_answer and changemapserverack.
Correct minor mistakes as pointed by MishimaHaruna
Merge pull request #251 from panikon/master

Function types behaviour