perf_counter tools: Generate per command manpages (and pdf/html, etc.)

Import Git's nice .txt => {man/html/pdf} generation machinery.

Fix various errors in the Documentation/perf*.txt description as well.

Also fix a bug in builtin-help: we'd map 'perf help top' to 'perftop'
if only the 'perf' binary is in the default PATH - confusing the manpage
logic. I dont fully understand why Git did it this way - but i suppose
it's a migration artifact from their migration from standalone git-xyz
commands to 'git xyz' commands. The perf tools were always using the
modern form so it's not an issue there.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/perf_counter/Documentation/perf.txt b/Documentation/perf_counter/Documentation/perf.txt
new file mode 100644
index 0000000..e3d8b38
--- /dev/null
+++ b/Documentation/perf_counter/Documentation/perf.txt
@@ -0,0 +1,23 @@
+perf(1)
+=======
+
+NAME
+----
+perf - Performance analysis tools for Linux
+
+SYNOPSIS
+--------
+[verse]
+'perf' [--version] [--help] COMMAND [ARGS]
+
+DESCRIPTION
+-----------
+Performance counters for Linux are are a new kernel-based subsystem
+that provide a framework for all things performance analysis. It
+covers hardware level (CPU/PMU, Performance Monitoring Unit) features
+and software features (software counters, tracepoints) as well.
+
+SEE ALSO
+--------
+linkperf:perf-stat[1], linkperf:perf-top[1],
+linkperf:perf-record[1], linkperf:perf-report[1]