patch 9.0.1257: code style is not check in test scripts

Problem:    Code style is not check in test scripts.
Solution:   Add basic code style check for test files.
diff --git a/src/testdir/test_map_functions.vim b/src/testdir/test_map_functions.vim
index 13e61f2..a750cd7 100644
--- a/src/testdir/test_map_functions.vim
+++ b/src/testdir/test_map_functions.vim
@@ -1,7 +1,7 @@
 " Tests for maparg(), mapcheck(), mapset(), maplist()
 " Also test utf8 map with a 0x80 byte.
 
-func s:SID()     
+func s:SID()
   return str2nr(matchstr(expand('<sfile>'), '<SNR>\zs\d\+\ze_SID$'))
 endfunc
 
@@ -18,7 +18,7 @@
   call assert_equal({'silent': 0, 'noremap': 0, 'script': 0, 'lhs': 'foo<C-V>',
         \ 'lhsraw': "foo\x80\xfc\x04V", 'lhsrawalt': "foo\x16",
         \ 'mode': ' ', 'nowait': 0, 'expr': 0, 'sid': sid, 'scriptversion': 1,
-        \ 'lnum': lnum + 1, 
+        \ 'lnum': lnum + 1,
 	\ 'rhs': 'is<F4>foo', 'buffer': 0, 'abbr': 0, 'mode_bits': 0x47},
 	\ maparg('foo<C-V>', '', 0, 1))
   call assert_equal({'silent': 1, 'noremap': 1, 'script': 1, 'lhs': 'bar',