Correct and update the Warpin installation script

[John Small]

1. There is a minor syntax error which prevents Warpin from checking for the required minimum version of itself.
2. There is a grammatic error in some of the text.
3. Some text is out-of-date, referring to the "first" version of FM/2 built with Open Watcom.

[John Small]

Added to ticket:

SED command improvements SVN property settings Miscellaneous code cleanup