Convert parse_option to sh, use Perl instead of awk, implement --help.

t/lib/samples/bash/help001.txt

@@ -0,0 +1,30 @@
+Usage: pt-stalk [OPTIONS] [-- MYSQL_OPTIONS]
+
+For more information, 'man pt-stalk' or 'perldoc /Users/daniel/p/bash-tool-libs/t/lib/samples/bash/po001.sh'.
+
+Command line options:
+
+--help
+  Print help and exit.
+
+--int-opt
+  Int option without a default.
+
+--int-opt2
+  Int option with a default.
+
+--noption
+  Negatable option.
+
+--string-opt
+  String option without a default.
+
+--string-opt2
+  String option with a default.
+
+--typeless-option
+  Just an option.
+
+--version
+  Print tool's version and exit.
+

t/lib/samples/bash/po001.sh

@@ -110,11 +110,13 @@ Just an option.
 
 default: yes; negatable: yes
 
+Negatable option.
+
 =item --int-opt
 
 type: int
 
-Int option without a default
+Int option without a default.
 
 =item --int-opt2
 
@@ -128,6 +130,10 @@ short form: -v
 
 Print tool's version and exit.
 
+=item --help
+
+Print help and exit.
+
 =back
 
 =head1 ENVIRONMENT