tools: bpftool: add option parsing to bpftool, --help and --version

Add an option parsing facility to bpftool, in prevision of future
options for demanding JSON output. Currently, two options are added:
--help and --version, that act the same as the respective commands
`help` and `version`.

Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
index 69b3770..6620a81 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst
@@ -50,6 +50,14 @@
 	**bpftool prog help**
 		  Print short help message.
 
+OPTIONS
+=======
+	-h, --help
+		  Print short generic help message (similar to **bpftool help**).
+
+	-v, --version
+		  Print version number (similar to **bpftool version**).
+
 EXAMPLES
 ========
 **# bpftool prog show**