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>

tools/bpf/bpftool/Documentation/bpftool-map.rst

@@ -68,6 +68,14 @@ DESCRIPTION
 	**bpftool map 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 map show**

tools/bpf/bpftool/Documentation/bpftool-prog.rst

@@ -50,6 +50,14 @@ DESCRIPTION
 	**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**

tools/bpf/bpftool/Documentation/bpftool.rst

@@ -31,6 +31,14 @@ DESCRIPTION
 	Note that format of the output of all tools is not guaranteed to be
 	stable and should not be depended upon.
 
+OPTIONS
+=======
+	-h, --help
+		  Print short help message (similar to **bpftool help**).
+
+	-v, --version
+		  Print version number (similar to **bpftool version**).
+
 SEE ALSO
 ========
 	**bpftool-map**\ (8), **bpftool-prog**\ (8)