Make monitor and joystick names static strings

Related to #478.

(cherry picked from commit da236ba807)

src/internal.h

@@ -423,7 +423,7 @@ struct _GLFWwindow
 //
 struct _GLFWmonitor
 {
-    char*           name;
+    char            name[128];
     void*           userPointer;
 
     // Physical dimensions in millimeters.
@@ -484,7 +484,7 @@ struct _GLFWjoystick
     int             buttonCount;
     unsigned char*  hats;
     int             hatCount;
-    char*           name;
+    char            name[128];
     void*           userPointer;
     char            guid[33];
     _GLFWmapping*   mapping;