calc: sort+headers: don't use GNU sed.

Implement unbuffered input to avoid GNU sed dependency.
calc: bugfix on --sort without grouping.

'pipe_through_sort' was not cleared, caused errors on FreeBSD
(all other systems seems not to mind calling pclose on a non-popen
FILE).
TravisCI - no need for GNU Sed 4.2.2 anymore.
Merge branch 'no_sed' into TravisMacOSX4