Fix libGL not being found on NetBSD

Fixes #646.

README.md

@@ -82,6 +82,7 @@ used by the tests and examples and are not required to build the library.
  - [WGL] Removed dependency on external WGL headers
  - [GLX] Replaced legacy renderable with `GLXWindow`
  - [GLX] Removed dependency on external GLX headers
+ - [GLX] Bugfix: NetBSD does not provide `libGL.so.1`
  - [EGL] Removed dependency on external EGL headers
 
 

src/glx_context.c

@@ -151,20 +151,33 @@ static GLXContext createLegacyContext(_GLFWwindow* window,
 // Initialize GLX
 //
 int _glfwInitContextAPI(void)
+{
+    int i;
+    const char* sonames[] =
     {
 #if defined(__CYGWIN__)
-    const char* soname = "libGL-1.so";
+        "libGL-1.so",
 #else
-    const char* soname = "libGL.so.1";
+        "libGL.so.1",
+        "libGL.so",
 #endif
+        NULL
+    };
+
 
     if (!_glfwCreateContextTLS())
         return GLFW_FALSE;
 
-    _glfw.glx.handle = dlopen(soname, RTLD_LAZY | RTLD_GLOBAL);
+    for (i = 0;  sonames[i];  i++)
+    {
+        _glfw.glx.handle = dlopen(sonames[i], RTLD_LAZY | RTLD_GLOBAL);
+        if (_glfw.glx.handle)
+            break;
+    }
+
     if (!_glfw.glx.handle)
     {
-        _glfwInputError(GLFW_API_UNAVAILABLE, "GLX: %s", dlerror());
+        _glfwInputError(GLFW_API_UNAVAILABLE, "GLX: Failed to load GLX");
         return GLFW_FALSE;
     }