[PATCH] tc: fix build with flex>=2.6.5

[ojab <ojab@ojab.ru>]

Since flex-2.6.5 [1] `yyunput` takes a single argument and build fails
with:
```
emp_ematch.l:35:69: error: macro ‘yyunput’ passed 2 arguments, but takes just 1
   35 |  static void __attribute__ ((unused)) yyunput (int c,char *buf_ptr  );
      |                                                                     ^
emp_ematch.lex.c:466:9: note: macro ‘yyunput’ defined here
  466 | #define yyunput(c) yyunput_r( c, (yytext_ptr)  )
      |         ^~~~~~~
emp_ematch.l:35:39: error: variable or field ‘yyunput’ declared void
   35 |  static void __attribute__ ((unused)) yyunput (int c,char *buf_ptr  );
      |                                       ^~~~~~~
emp_ematch.lex.c:1836:13: warning: ‘yyunput_r’ defined but not used [-Wunused-function]
 1836 | static void yyunput_r (int c, char * yy_bp )
      |             ^~~~~~~~~
make[1]: *** [../config.mk:34: emp_ematch.lex.o] Error 1
```

Use new `YY_NO_YYUNPUT` to silence redefinition warning in this case
and skip `__attribute__ ((unused))`.

[1] https://github.com/westes/flex/commit/721622ea6e6aaf3aa7e55d939679f21e98b76d86

Signed-off-by: ojab <ojab@ojab.ru>
---
 tc/emp_ematch.l | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tc/emp_ematch.l b/tc/emp_ematch.l
index 2f4926d4..c6fd907e 100644
--- a/tc/emp_ematch.l
+++ b/tc/emp_ematch.l
@@ -10,6 +10,7 @@
 
  #define NEXT_EM_ARG() do { ematch_argc--; ematch_argv++; } while(0);
 
+ #define YY_NO_YYUNPUT 1
  #define YY_INPUT(buf, result, max_size)				\
  {									\
  next:									\
@@ -32,7 +33,9 @@
 	}								\
  }
 
- static void __attribute__ ((unused)) yyunput (int c,char *buf_ptr  );
+ #ifndef yyunput
+ static void __attribute__ ((unused)) yyunput (int c, char *buf_ptr);
+ #endif
  static void __attribute__ ((unused)) yy_push_state (int  new_state );
  static void __attribute__ ((unused)) yy_pop_state  (void);
  static int  __attribute__ ((unused)) yy_top_state (void );
-- 
2.53.0