Disambiguate IsRectVisible() variants

[ocornut]

Again, small issue but right now I can't seem to find how to proceed. May be trivial:

Current output:

CIMGUI_API bool ImGui_IsRectVisible(ImVec2 size);                             // test if rectangle (of given size, starting from cursor position) is visible / not clipped.
CIMGUI_API bool ImGui_IsRectVisibleImVec2(ImVec2 rect_min, ImVec2 rect_max);  // test if rectangle (in screen space) is visible / not clipped. to perform coarse clipping on user's side.

it's an odd situation in the public API (and probably not a good API to be honest) but ideally in cimgui it would be:

CIMGUI_API bool  ImGui_IsRectVisibleBySize(ImVec2 size);                 // test if rectangle (of given size, starting from cursor position) is visible / not clipped.
CIMGUI_API bool  ImGui_IsRectVisible(ImVec2 rect_min, ImVec2 rect_max);  // test if rectangle (in screen space) is visible / not clipped. to perform coarse clipping on user's side.

[ShironekoBen]

OK, I've added some special-case renaming rules to do that.

[ocornut]

Looks good, thank you!