Make smoother use in GitHub

+x bison.exe, remove some extra files in runtests, and ignore more
created files.
diff --git a/Test/runtests b/Test/runtests
old mode 100755
new mode 100644
index 09368f1..db2a345
--- a/Test/runtests
+++ b/Test/runtests
@@ -53,6 +53,7 @@
       ;;
   esac
 done < test-spirv-list
+rm -f comp.spv frag.spv geom.spv tesc.spv tese.spv vert.spv
 
 #
 # Preprocessor tests