gzip: code shrink

gzip: code shrink

huft_build() still has way too many params

function                                             old     new   delta
lit                                                    -      94     +94
dist                                                   -      94     +94
huft_build                                          1058    1054      -4
inflate_block                                       1281    1254     -27
cpdext                                                30       -     -30
cplext                                                31       -     -31
cpdist                                                60       -     -60
cplens                                                62       -     -62
------------------------------------------------------------------------------
(add/remove: 2/4 grow/shrink: 0/2 up/down: 188/-214)          Total: -26 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>