fixing malloc and realloc so it return right value

fixing malloc and realloc so it return right value
do not mix the doc over malloc and realloc. Thanks filip
<filip2307> malloc(0) -> valid buffer
<GreatLord> then I revert that change
<filip2307> realloc(<non-null pointer>, 0) -> NULL
<filip2307> realloc(NULL, 0) -> valid buffer

svn path=/trunk/; revision=22197