Core library clean up: Make range expressions more consistent and replace uses of .. with ..=

core/os/file_windows.odin

@@ -347,7 +347,7 @@ is_abs :: proc(path: string) -> bool {
 	when ODIN_OS == "windows" {
 		if len(path) > 2 {
 			switch path[0] {
-			case 'A'..'Z', 'a'..'z':
+			case 'A'..='Z', 'a'..='z':
 				return path[1] == ':' && is_path_separator(path[2]);
 			}
 		}

core/os/os2/stat_windows.odin

@@ -322,7 +322,7 @@ _is_abs :: proc(path: string) -> bool {
 	}
 	if len(path) > 2 {
 		switch path[0] {
-		case 'A'..'Z', 'a'..'z':
+		case 'A'..='Z', 'a'..='z':
 			return path[1] == ':' && is_path_separator(path[2]);
 		}
 	}