perf tools: Remove 'perf' from subcmd function and variable names

In preparation for moving exec_cmd.c and run-command.c out of perf and
into a library, remove 'perf' from all the symbol names.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/bc3ee82b40b8f396b644fa49e0f7260ce442635b.1450193761.git.jpoimboe@redhat.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>