Small fix; when pulldown menus are too large to display (they get aligned

with top/bottom to active button) the menu aligns from bottom of blender
window.

This already happened for File->Export menu

source/blender/src/interface.c

@@ -697,6 +697,12 @@ static void ui_positionblock(uiBlock *block, uiBut *but)
 			}
 		}
 
+		/* and now we handle the exception; no space below or to right */
+		if(top==0 && down==0) {
+			// align with bottom of screen 
+			yof= ysize;
+		}
+		
 		// apply requested offset in the block
 		xof += block->xofs/block->aspect;
 		yof += block->yofs/block->aspect;