[minor] several corrigendum for Language Reference 3.0

[gdelconti]

chr():
Will return a character for the given number.
Bla = chr({string or var name}) -> SHOULD BE: Bla = chr({value or var name})

int():
Will return an integer value.
int({string or var name}) -> SHOULD BE: int({value or var name})

oct():
Will return the oct value of an integer.
oct({string or var name}) -> SHOULD BE: oct({value or var name})

hex():
Will return the hex value of an integer.
An optional 2nd argument define the number of digits
hex({string or var name},{nb_of_digits}) -> SHOULD BE: hex({value or var name},{nb_of_digits})