check for tcgetpgrp() presence before using.

configure.ac

@@ -235,6 +235,6 @@ XMP_TRY_COMPILE(whether compiler understands -Wunused-result,
   int main(){}],
   CFLAGS="${CFLAGS} -Wno-unused-result")  
 
-AC_CHECK_FUNCS(kill getopt_long)
+AC_CHECK_FUNCS(kill getopt_long tcgetpgrp)
 AC_CONFIG_FILES([Makefile src/Makefile])
 AC_OUTPUT

src/main.c

@@ -83,7 +83,7 @@ static void sigtstp_handler(int n)
 
 static void sigcont_handler(int sig)
 {
-#ifdef HAVE_TERMIOS_H
+#if defined(HAVE_TERMIOS_H) && defined(HAVE_TCGETPGRP)
 	unsigned int old_in = foreground_in;
 
 	foreground_in  = tcgetpgrp(STDIN_FILENO)  == getpgrp();