Fixed bug #65947 (basename is no more working after fgetcsv in certain situation)

previous codes: "#define php_mblen(ptr, len) ((ptr) == NULL ? mbsinit(&BG(mblen_state)):
(int)mbrlen(ptr, len, &BG(mblen_state)))#

it use mbsinit there, seems try to initialize the mblen_state, but:
"This function does not change the state identified by ps. Typical ways
to make the state pointed by ps an initial state are:

memset (ps,0,sizeof(*ps));  // ps points to zero-valued object
"
http://www.cplusplus.com/reference/cwchar/mbsinit/?kw=mbsinit