refactoring, update ci build scripts, etc

- cache results of CompareWindowsVersion() to shared variables to cut
down on redundant calls
- apply appveyor build version to artifacts (wip, could be broken)
- add .gitattributes
- finish patternfind.c (snr funcs unused, untested)
- delete COPYING.txt (it is created from LICENSE during the build
process)

wufuc.sln

@@ -7,6 +7,7 @@ Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "wufuc", "wufuc\wufuc.vcxpro
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Solution Items", "Solution Items", "{8C2147FF-2B83-479B-813E-5ACB86F43042}"
 	ProjectSection(SolutionItems) = preProject
+		.gitattributes = .gitattributes
 		.gitignore = .gitignore
 		appveyor.yml = appveyor.yml
 		LICENSE = LICENSE