add Rscons.glob - close #50

build_tests/build_dir/Rsconsfile

@@ -1,5 +1,5 @@
 Rscons::Environment.new do |env|
-  env.append('CPPPATH' => Dir['src/**/*/'].sort)
+  env.append('CPPPATH' => Rscons.glob('src/**'))
   env.build_dir(%r{^src/([^/]+)/}, 'build_\\1/')
-  env.Program('build_dir.exe', Dir['src/**/*.c'])
+  env.Program('build_dir.exe', Rscons.glob('src/**/*.c'))
 end