vcl: clean up before error returns in OpenGLContext::ImplInit()

JunitTest_chart_unoapi fails here with "assert(!hasCurrent())" because
the initialization apparently fails due to lack of a
wglCreateContextAttribsARB in the VM, so ensure that the hTempRC is not
active and also deleted in all cases.

(cherry picked from commit 5efad739)

vcl: even in the newfangled OpenGL world, initializing members is ...
... still a good idea.
(cherry picked from commit 37d24365)

Change-Id: I7e03b95d1146af48a24e34692c3c2827298fccee
Reviewed-on: https://gerrit.libreoffice.org/19040Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

include/vcl/opengl/OpenGLContext.hxx

@@ -142,6 +142,9 @@ struct GLWindow
     GLWindow()
         :
 #if defined( _WIN32 )
+        hWnd(NULL),
+        hDC(NULL),
+        hRC(NULL),
 #elif defined( MACOSX )
 #elif defined( IOS )
 #elif defined( ANDROID )

vcl/source/opengl/OpenGLContext.cxx

@@ -960,14 +960,22 @@ bool OpenGLContext::ImplInit()
     }
 
     if (!InitGLEW())
+    {
+        wglMakeCurrent(NULL, NULL);
+        wglDeleteContext(hTempRC);
         return false;
+    }
 
     HGLRC hSharedCtx = 0;
     if (!g_vShareList.empty())
         hSharedCtx = g_vShareList.front();
 
     if (!wglCreateContextAttribsARB)
+    {
+        wglMakeCurrent(NULL, NULL);
+        wglDeleteContext(hTempRC);
         return false;
+    }
 
     // now setup the shared context; this needs a temporary context already
     // set up in order to work
@@ -983,6 +991,8 @@ bool OpenGLContext::ImplInit()
     {
         ImplWriteLastError(GetLastError(), "wglCreateContextAttribsARB in OpenGLContext::ImplInit");
         SAL_WARN("vcl.opengl", "wglCreateContextAttribsARB failed");
+        wglMakeCurrent(NULL, NULL);
+        wglDeleteContext(hTempRC);
         return false;
     }