iconv(1) don't initialize iconv_t when reuse each file conversion.

[Takehiko NOZAKI]

iconv(1) flush iconv_t by iconv(cd, NULL, NULL, out, outsz). but some stateful encoding may end up with 'stable' state(not 'initial' state).

so full initialize iconv(cd, NULL, NULL, NULL, NULL) is required.

[Takehiko NOZAKI]

BUGFIX: Issue #74 -- iconv(1) don't initialize iconv_t when reuse each file conversion.

→ <<cset 496566e8df19>>