shrink sha hashing a bit more (remove wbuflen field from ctx),

shrink sha hashing a bit more (remove wbuflen field from ctx),
remove the requirement for aligned buffer

function                                             old     new   delta
sha512_hash                                          262     297     +35
sha1_end                                             136     143      +7
passwd_main                                         1019    1023      +4
sha256_end                                           135     137      +2
count_lines                                           72      74      +2
sha256_hash                                          259     260      +1
popstring                                            164     158      -6
sha512_begin                                          88      81      -7
sha256_begin                                          44      37      -7
parse_expr                                           832     824      -8
bbunpack                                             446     438      -8
sha256_process_block64                               529     520      -9
md5_end                                              166     151     -15
evaltreenr                                           817     802     -15
evaltree                                             817     802     -15
sha512_end                                           204     182     -22
sha512_process_block128                             1444    1405     -39
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 6/11 up/down: 51/-151)         Total: -100 bytes