runtime(syntax-tests): Retrofit input/c.c. with TEST_SETUP

Also:

- Include a syntax test for Markdown that takes advantage of
  a sourceable setup configuration.
- Update Filelist

closes: #14215

Signed-off-by: Aliaksei Budavei <0x000c70@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/syntax/testdir/dumps/c_06.dump

@@ -1,9 +1,10 @@
-| +0&#ffffff0@3|/+0#0000e05&|*| +0#0000000&@68
+| +0&#ffffff0@74
+@4|/+0#0000e05&|*| +0#0000000&@68
 | +0#0000e05&@4|*| |D|o| |a|n|y| |s|y|s|t|e|m|-|s|p|e|c|i|f|i|c| |i|n|i|t|i|a|l|i|s|a|t|i|o|n|s|.| @1|T|h|e|s|e| |c|a|n| |N|O|T| |u|s|e| |I|O|b|u|f@1| |o|r
 | @4|*| |N|a|m|e|B|u|f@1|.| @1|T|h|u|s| |e|m|s|g|2|(|)| |c|a|n@1|o|t| |b|e| |c|a|l@1|e|d|!| +0#0000000&@26
 | +0#0000e05&@4|*|/| +0#0000000&@67
-@4|m|c|h|_|e|a|r|l|y|_|i|n|i|t|(|)|;| @53
-> @74
+@4>m|c|h|_|e|a|r|l|y|_|i|n|i|t|(|)|;| @53
+@75
 @4|/+0#0000e05&@1| |S|o|u|r|c|e| |s|t|a|r|t|u|p| |s|c|r|i|p|t|s|.| +0#0000000&@44
 @4|s|o|u|r|c|e|_|s|t|a|r|t|u|p|_|s|c|r|i|p|t|s|(|&|p|a|r|a|m|s|)|;| @38
 @75
@@ -16,5 +17,4 @@
 |#+0#e000e06&|e|l|s|e| +0#0000000&@69
 @4|r+0#af5f00255&|e|t|u|r|n| +0#0000000&|v|i|m|_|m|a|i|n|2|(|)|;| @51
 |#+0#e000e06&|e|n|d|i|f| +0#0000000&@68
-|}| @73
-@57|1|0|9|,|0|-|1| @6|B|o|t| 
+@57|1|0|9|,|5| @8|9@1|%|