no need to do that for all contexts

This fixes a crash as we would need to make each context current before
calling ReleaseFramebuffers.

However this is totally unnecessary as only the current context can have
bound framebuffers.

Change-Id: I8b1496bb890982742b3d2ebf60fdce47db642d70

include/vcl/opengl/OpenGLContext.hxx

@@ -200,9 +200,6 @@ public:
 
     bool isCurrent();
     static void clearCurrent();
-    /// reset all contexts dis-associating them with their underlying
-    /// resources before a potential thread switch.
-    static void resetAllContexts();
 
     /// make this GL context current - so it is implicit in subsequent GL calls
     void makeCurrent();

vcl/generic/app/geninst.cxx

@@ -55,7 +55,7 @@ void SalYieldMutex::release()
     {
         if ( mnCount == 1 )
         {
-            OpenGLContext::resetAllContexts();
+            OpenGLContext::clearCurrent();
             mnThreadId = 0;
         }
         mnCount--;

vcl/source/opengl/OpenGLContext.cxx

@@ -1292,22 +1292,6 @@ void OpenGLContext::clearCurrent()
         pCurrentCtx->ReleaseFramebuffers();
 }
 
-void OpenGLContext::resetAllContexts()
-{
-    ImplSVData* pSVData = ImplGetSVData();
-
-    // release all framebuffers from the old context so we can re-attach the
-    // texture in the new context
-    for (OpenGLContext* l = pSVData->maGDIData.mpLastContext; l;
-         l = l->mpPrevContext)
-    {
-        l->ReleaseFramebuffers();
-        if (l->isCurrent())
-            l->resetCurrent();
-        assert (!l->mpNextContext || l->mpNextContext->mpPrevContext == l);
-    }
-}
-
 void OpenGLContext::makeCurrent()
 {
     ImplSVData* pSVData = ImplGetSVData();