patch 8.0.0147: searchpair() fails when 'magic' is off

Problem:    searchpair() does not work when 'magic' is off. (Chris Paul)
Solution:   Add \m in the pattern. (Christian Brabandt, closes #1341)
diff --git a/src/testdir/test_search.vim b/src/testdir/test_search.vim
index 3b9aff4..040a809 100644
--- a/src/testdir/test_search.vim
+++ b/src/testdir/test_search.vim
@@ -279,3 +279,18 @@
   call X()
   bwipe!
 endfunc
+
+func Test_searchpair()
+  new
+  call setline(1, ['other code here', '', '[', '" cursor here', ']'])
+  4
+  let a=searchpair('\[','',']','bW')
+  call assert_equal(3, a)
+  set nomagic
+  4
+  let a=searchpair('\[','',']','bW')
+  call assert_equal(3, a)
+  set magic
+  q!
+endfunc
+