less: fix bugs discovered with "git log -p | less -m" on kernel tree

function                                             old     new   delta
read_lines                                           685     733     +48

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
libbb: provide usleep() fallback implementation

POSIX.1-2008 removed the usleep function, provide a fallback
implementaion using the recommended nanosleep().

Signed-off-by: Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
ash,hush: set $HOSTNAME is bash compat. Closes 7028

function                                             old     new   delta
hush_main                                           1056    1128     +72
ash_main                                            1442    1487     +45

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
libbb/obscure.c: code shrink. Suggested by Tito.

function                                             old     new   delta
string_checker                                        97      92      -5

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
adjtimex: make its help text and printed data a bit less cryptic

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