patch 8.1.2156: first character after Tab is not highlighted

Problem:    First character after Tab is not highlighted.
Solution:   Remember the syntax attribute for a column.
diff --git a/src/testdir/dumps/Test_syntax_c_01.dump b/src/testdir/dumps/Test_syntax_c_01.dump
index 2fea5d6..54e34a6 100644
--- a/src/testdir/dumps/Test_syntax_c_01.dump
+++ b/src/testdir/dumps/Test_syntax_c_01.dump
@@ -12,9 +12,9 @@
 |}| @73
 @3|s+0#00e0003&|t|a|t|i|c| +0#0000000&|v+0#00e0003&|o|i|d| +0#0000000&@60
 |m|y|F|u|n|c|t|i|o|n|(|c+0#00e0003&|o|n|s|t| +0#0000000&|d+0#00e0003&|o|u|b|l|e| +0#0000000&|c|o|u|n|t|,| |s+0#00e0003&|t|r|u|c|t| +0#0000000&|n|o|t|h|i|n|g|,| |l+0#00e0003&|o|n|g| +0#0000000&|t|h|e|r|e|)| |{| @14
-@2|/+0#0000e05&@1| |1+0#e000002&|2|3|:+0#0000e05&| |n|o|t|h|i|n|g| |t|o| |r|e|a|d| |h|e|r|e| +0#0000000&@44
-@2|f+0#af5f00255&|o|r| +0#0000000&|(|i+0#00e0003&|n|t| +0#0000000&|i| |=| |0+0#e000002&|;+0#0000000&| |i| |<| |c|o|u|n|t|;| |+@1|i|)| |{| @39
-@4|b+0#af5f00255&|r|e|a|k|;+0#0000000&| @64
-@2|}| @71
+@1| +0#0000e05&@6|/@1| |1+0#e000002&|2|3|:+0#0000e05&| |n|o|t|h|i|n|g| |t|o| |r|e|a|d| |h|e|r|e| +0#0000000&@38
+@1| +0#af5f00255&@6|f|o|r| +0#0000000&|(|i+0#00e0003&|n|t| +0#0000000&|i| |=| |0+0#e000002&|;+0#0000000&| |i| |<| |c|o|u|n|t|;| |+@1|i|)| |{| @33
+@11|b+0#af5f00255&|r|e|a|k|;+0#0000000&| @57
+@8|}| @65
 |}| @73
-|"|X|t|e|s|t|.|c|"| |1|9|L|,| |3|6|4|C| @37|1|,|1| @10|A|l@1| 
+|"|X|t|e|s|t|.|c|"| |1|9|L|,| |3|6|1|C| @37|1|,|1| @10|A|l@1| 
diff --git a/src/testdir/test_syntax.vim b/src/testdir/test_syntax.vim
index 0479901..c7d6f2d 100644
--- a/src/testdir/test_syntax.vim
+++ b/src/testdir/test_syntax.vim
@@ -551,10 +551,10 @@
 	\ '}',
 	\ '   static void',
 	\ 'myFunction(const double count, struct nothing, long there) {',
-	\ '  // 123: nothing to read here',
-	\ '  for (int i = 0; i < count; ++i) {',
-	\ '    break;',
-	\ '  }',
+	\ "\t// 123: nothing to read here",
+	\ "\tfor (int i = 0; i < count; ++i) {",
+	\ "\t   break;",
+	\ "\t}",
 	\ '}',
 	\ ], 'Xtest.c')