build: move an #include to where it is needed

src/nano.c

@@ -33,6 +33,7 @@
 #include <langinfo.h>
 #endif
 #include <locale.h>
+#include <signal.h>
 #include <string.h>
 #ifdef HAVE_TERMIOS_H
 #include <termios.h>

src/nano.h

@@ -119,7 +119,6 @@
 #include <sys/stat.h>
 #include <dirent.h>
 #include <regex.h>
-#include <signal.h>
 
 /* If we aren't using an ncurses with mouse support, exclude any
  * mouse routines, as they are useless then. */

src/text.c

@@ -27,6 +27,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <signal.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/wait.h>