Waf: Be more explicit in patterns

Waf.gitignore

@@ -1,4 +1,9 @@
-.waf-*
-.waf3-*
-.lock-*
 # For projects that use the Waf build system: https://waf.io/
+# Dot-hidden on Unix-like systems
+.waf-*-*/
+.waf3-*-*/
+# Hidden directory on Windows (no dot)
+waf-*-*/
+waf3-*-*/
+# Lockfile
+.lock-waf_*_build