man3/*: srcfix: fix warnings from "mandoc -Tlint"

man3/*: srcfix: fix warnings from "mandoc -Tlint"

Remove superfluous paragraph macros.

Remove request ".br" if it precedes a line, that begins with a
space, as such lines automatically cause a break.

There is no change in the output from "nroff" and "groff".

###

Examples of warnings from "mandoc -Tlint":

mandoc: bindresvport.3:41:2: WARNING: skipping paragraph macro: PP after SH

mandoc: crypt.3:228:2: WARNING: skipping paragraph macro: PP empty

mandoc: dlinfo.3:151:2: WARNING: skipping paragraph macro: IP empty

mandoc: exec.3:86:2: WARNING: skipping paragraph macro: PP after SS

mandoc: getsubopt.3:45:2: WARNING: skipping paragraph macro: br before text line with leading blank

Signed-off-by: Bjarni Ingi Gislason <bjarniig@rhi.hi.is>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>