perf ui browser: Fix ui popup argv browser for many entries

Fix the argv ui browser code to correctly display more entries than fit
on the screen without crashing. The problem was some type confusion with
pointer types in the ->seek function. Do the argv arithmetic correctly
with char ** pointers. Also add some asserts to find overruns and limit
the display function correctly.

Then finally remove a workaround for this in the res sample browser.

Committer testing:

1) Resize the x terminal to have just some 5 lines

2) Use 'perf report --samples 1' to activate the sample browser options
   in the menu

3) Press ENTER, this will cause the crash:

  # perf report --samples 1
  perf: Segmentation fault
  -------- backtrace --------
  perf[0x5a514a]
  /lib64/libc.so.6(+0x385bf)[0x7f27281b55bf]
  /lib64/libc.so.6(+0x161a67)[0x7f27282dea67]
  /lib64/libslang.so.2(SLsmg_write_wrapped_string+0x82)[0x7f272874a0b2]
  perf(ui_browser__argv_refresh+0x77)[0x5939a7]
  perf[0x5924cc]
  perf(ui_browser__run+0x39)[0x593449]
  perf(ui__popup_menu+0x83)[0x5a5263]
  perf[0x59f421]
  perf(perf_evlist__tui_browse_hists+0x3a0)[0x5a3780]
  perf(cmd_report+0x2746)[0x447136]
  perf[0x4a95fe]
  perf(main+0x61c)[0x42dc6c]
  /lib64/libc.so.6(__libc_start_main+0xf2)[0x7f27281a1412]
  perf(_start+0x2d)[0x42de9d]
  #

After applying this patch no crash takes place in such situation.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: http://lkml.kernel.org/r/20190311144502.15423-12-andi@firstfloor.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>