Add helper script for porting vim patches.
Merge pull request #1513 from fwalch/vimpatch-script

Add helper script for porting vim patches.
Remove win16 references
Remove NeXTSTEP references
Remove Atari MiNT references
Remove OS/2 references

NOTE: Paul Slootman was removed from the top of os_unix.c but is still
credited somewhere in the docs dir...
Remove Windows 95 references
Remove BeOS/Haiku references
Remove initial VMS references