printf: fix %b, fix several bugs in %*.*, fix compat issues with

printf: fix %b, fix several bugs in %*.*, fix compat issues with
 aborting too early, support %zd; expand testsuite

function                                             old     new   delta
get_width_prec                                         -      46     +46
multiconvert                                          82      99     +17
conv_strtod                                           44      54     +10
print_direc                                          382     391      +9
printf_main                                          629     633      +4
conv_strtoul                                          20      16      -4
conv_strtol                                           20      16      -4
my_xstrtoul                                           20       -     -20
my_xstrtol                                            20       -     -20
my_xstrtod                                            21       -     -21
------------------------------------------------------------------------------
(add/remove: 1/3 grow/shrink: 4/2 up/down: 86/-69)             Total: 17 bytes