tests: fix compilation of tests on FreeBSD 11

Some includes were missing in .h files, and the tests must be linked
with intl and execinfo on FreeBSD.

src/gui/gui-chat.h

@@ -20,6 +20,8 @@
 #ifndef WEECHAT_GUI_CHAT_H
 #define WEECHAT_GUI_CHAT_H 1
 
+#include <time.h>
+
 struct t_hashtable;
 struct t_gui_window;
 struct t_gui_buffer;

src/gui/gui-key.h

@@ -20,6 +20,8 @@
 #ifndef WEECHAT_GUI_KEY_H
 #define WEECHAT_GUI_KEY_H 1
 
+#include <time.h>
+
 struct t_hashtable;
 
 #define GUI_KEY_BUFFER_BLOCK_SIZE 256

src/gui/gui-line.h

@@ -20,6 +20,7 @@
 #ifndef WEECHAT_GUI_LINE_H
 #define WEECHAT_GUI_LINE_H 1
 
+#include <time.h>
 #include <regex.h>
 
 struct t_infolist;