perf hists: Do column alignment on the format iterator

perf hists: Do column alignment on the format iterator

We were doing column alignment in the format function for each cell,
returning a string padded with spaces so that when the next column is
printed the cursor is at its column alignment.

This ends up needlessly printing trailing spaces, do it at the format
iterator, that is where we know if it is needed, i.e. if there is more
columns to be printed.

This eliminates the need for triming lines when doing a dump using 'P'
in the TUI browser and also produces far saner results with things like
piping 'perf report' to 'less'.

Right now only the formatters for sym->name and the 'locked' column
(perf mem report), that are the ones that end up at the end of lines
in the default 'perf report', 'perf top' and 'perf mem report' tools,
the others will be done in a subsequent patch.

In the end the 'width' parameter for the formatters now mean, in
'printf' terms, the 'precision', where before it was the field 'width'.

Reported-by: Dave Jones <davej@codemonkey.org.uk>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/n/tip-s7iwl2gj23w92l6tibnrcqzr@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>