tftpd: support full 512-byte requests

Some HP PA-RISC firmware always sends fixed 512-byte requests,
with trailing garbage.

function                                             old     new   delta
tftpd_main                                           578     572      -6

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
tftpd: tweak HP PA-RISC firmware bug compatibility

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
find: support -perm /BITS. Closes 7340

function                                             old     new   delta
parse_params                                        1487    1497     +10
func_perm                                             57      61      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 14/0)               Total: 14 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ash: factor out ASH_HELP config option

It used to be aliased to !FEATURE_SH_EXTRA_QUIET for ash,
while hush had it separate from FEATURE_SH_EXTRA_QUIET.

Bring ash in line with hush.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ash: fix off-by-one in "jobs %4" handling. closes 7310

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
mdev: treat zero-length /dev/mdev.seq the same as "\n" one. Closes 7334

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
vi: fix incorrect memory access on brace matching. Closes 7256

While at it, fix brace matching to actually show the match
(missed fflush was causing cursor positioning to be buffered);
shorten brace matching code; remove unused macro indirection
in indicate_error().

Custom linker script 'busybox_ldscript' found, using it
function                                             old     new   delta
indicate_error                                         -      61     +61
mysleep                                               43      56     +13
char_insert                                          483     486      +3
find_pair                                            167     124     -43
Indicate_Error                                        61       -     -61
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 2/1 up/down: 77/-104)           Total: -27 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ftpd: make LIST command show dotfiles too

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
sed: fix a buglet in s///NUM handling

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
df: implement -T option

function                                             old     new   delta
df_main                                              863     998    +135
packed_usage                                       29827   29861     +34
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 169/0)             Total: 169 bytes

Signed-off-by: Ari Sundholm <ari@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
false: make "false --help" exit with 1

function                                             old     new   delta
run_applet_no_and_exit                               447     445      -2

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