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)

.gitattributes

@@ -0,0 +1,23 @@
+* text=auto
+
+*.sln        text eol=crlf
+*.csproj     text eol=crlf
+*.vbproj     text eol=crlf
+*.vcxproj    text eol=crlf
+*.vcproj     text eol=crlf
+*.dbproj     text eol=crlf
+*.fsproj     text eol=crlf
+*.lsproj     text eol=crlf
+*.wixproj    text eol=crlf
+*.modelproj  text eol=crlf
+*.sqlproj    text eol=crlf
+*.wmaproj    text eol=crlf
+
+*.xproj      text eol=crlf
+*.props      text eol=crlf
+*.filters    text eol=crlf
+*.vcxitems   text eol=crlf
+
+*.rc         text eol=crlf
+*.bat        text eol=crlf
+*.cmd        text eol=crlf