* Serial Number / Activation Key (SN/AK) (SCO ODT Lite 3.0 / 3.2v4.2,
 * SCO OpenServer / 3.2v5.0.x):
 * -------------------------------------------------------------------
 *	Serial Number (SN):
 *		- 9 characters, normally 3 capital letters + 6 digits:
 *			"[A-Z]\{3,3\}[0-9]\{6,6\}"
 *		- the last character specifies the size of the next arithmetic shift of the 'si' 
 *		  variable to calculate the SN/AK checksum in the 'sn_ake_chksum()' function:
 *				shift = (last SN character) % 16
 *		  - since the last character is a digit in std. SN, the offset is usually [0-9]
 *
 *	Activation Key (AK):
 *		- 8 characters, 8 lowercase letters by default:
 *			"[a-z]\{8,8\}"
 *		  - in general we could describe AK as follows:
 *
 *			SCO v4.2:	<product_family.3><product_id.3><chksum.2>
 *			SCO v5.0.x:	<product_id.3><product_family.3><chksum.2>
 *
 *		    where:
 *				- <product_family> specifies the product family:
 *					- "cry" - Open Desktop (SCO v4.2)
 *					- "mfa" - OpenServer (SCO v5.0.x)
 *					  - but if for example 'xxx' is used, then 'imqm' after entering 
 *						'License Code' will also request 'License data'
 *			   	- <product_id> indicates the product itself, e.g.:
 *					- "aaa" - Open Desktop
 *					- "aae" - Open Desktop Lite
 *			   		- "aey" - OpenServer Desktop
 *			   		- "afa" - OpenServer Host
 *			   		- "afc" - OpenServer Enterprise
 *		- after encoding with the 'ak_encode(ak)' function,
 *			1) SCO v4.2:
 *			    the first 3 characters must be equal to <product_family> ("cry")
 *			    - the constant "cry" (SCO v4.2) is triggered by encoding (function
 *				  'ack_encode()') the "uiy" constant (SCO v4.2), which is hard-coded
 *				   in the 'iqm' application
 *			   SCO v5.0.x:
 *			    characters 4.-6. must be equal to <product_family> ("mfa")
 *			2) SCO v4.2:
 *			    characters 4.-6. must be one of the following strings (identification product):
 *				 - "aaa"		SCO Open Desktop
 *				 - "aab"		SCO Open Server Enterprise System (multiuser)
 *				 - "aae"		SCO Open Desktop Lite
 *				 - "aaf"		SCO Open Desktop Lite with Networking
 *				 - "aag"		SCO Open Server Enterprise System (16 user)
 *			   SCO v5.0.x:
 *			    the 1st to 3rd character must be one of the following strings (identification 
 *			    product):
 *			   	 - "aey"		SCO OpenServer Desktop
 *			   	 - "afa"		SCO OpenServer Host
 *			   	 - "afc"		SCO OpenServer Enterprise
 *			3) the last 2 characters (checksum) match the checksum sum ('sn_ake_chksum()') of 
 *			   SN + the part of the encoded AK without these 2 characters (i.e. without this 
 *			   checksum of course)
 *			- in other words, the encoded AK must be equal to the string:
 *		 
 *					"cryaa<product_id><chksum>"
 *		 
 *			  where <product_id> is one of the following: a, b, e, f, g
 *			  and <chksum> is equal to 'sn_ake_chksum("<SN>cryaa<product_id>")'