Renamed GetScrollPosY() to GetScrollY(). (#150)

Necessary to reduce confusion along with other scrolling functions,
because positions (e.g. cursor position) are not equivalent to scrolling
amount.

imgui.cpp

@@ -136,6 +136,7 @@
  Occasionally introducing changes that are breaking the API. The breakage are generally minor and easy to fix.
  Here is a change-log of API breaking changes, if you are using one of the functions listed, expect to have to fix some code.
  
+ - 2015/07/01 (1.42) - renamed GetScrollPosY() to GetScrollY(). Necessary to reduce confusion along with other scrolling functions, because positions (e.g. cursor position) are not equivalent to scrolling amount.
  - 2015/06/14 (1.41) - changed ImageButton() default bg_col parameter from (0,0,0,1) (black) to (0,0,0,0) (transparent) - makes a difference when texture have transparence
  - 2015/06/14 (1.41) - changed Selectable() API from (label, selected, size) to (label, selected, flags, size). Size override should have been rarely be used. Sorry!
  - 2015/05/31 (1.40) - renamed GetWindowCollapsed() to IsWindowCollapsed() for consistency. Kept inline redirection function (will obsolete).
@@ -4815,7 +4816,7 @@ void ImGui::SetCursorScreenPos(const ImVec2& screen_pos)
     window->DC.CursorPos = screen_pos;
 }
 
-float ImGui::GetScrollPosY()
+float ImGui::GetScrollY()
 {
     ImGuiWindow* window = GetCurrentWindow();
     return window->ScrollY;

imgui.h

@@ -135,7 +135,7 @@ namespace ImGui
     IMGUI_API void          SetWindowCollapsed(const char* name, bool collapsed, ImGuiSetCond cond = 0);   // set named window collapsed state
     IMGUI_API void          SetWindowFocus(const char* name);                                              // set named window to be focused / front-most. use NULL to remove focus.
 
-    IMGUI_API float         GetScrollPosY();                                                    // get scrolling position [0..GetScrollMaxY()]
+    IMGUI_API float         GetScrollY();                                                       // get scrolling position [0..GetScrollMaxY()]
     IMGUI_API float         GetScrollMaxY();                                                    // get maximum scrolling position == ContentSize.Y - WindowSize.Y
     IMGUI_API void          SetScrollPosHere(float center_y_ratio = 0.5f);                      // adjust scrolling position to make the current cursor position visible. center_y_ratio=0.0: top, =0.5: center, =1.0: bottom.
     IMGUI_API void          SetKeyboardFocusHere(int offset = 0);                               // focus keyboard on the next widget. Use positive 'offset' to access sub components of a multiple component widget