ImFont: CalcTextSizeA() fixed font scaling with fallback character.

InputText: fixed handling of scaled font. re-organized bits of code toward merging all sizes calculations (#200)

Fixed framerate counter averaging buffer size (shouldn't have been included in previous commit)

InputText(): removed extraneous CalcTextSizeW call for tracking cursor/scrolling, remove spike (#200)

InputText(): char width calculation calls font->GetCharAdvance() directly (#200)

ImFont::RenderText() faster handling of rendering above clipping rect (useful for #200)

InputText() clear selection when using undo/redo (#200)

InputText() tidying up (#200)

InputTextMultiline() preserve activeid/cursor/selection when using scrollbar + tidying up (#200)

Speeding up some wchar<>UTF8 functions and some specialization for Ascii. (testing 500 KB text for #200)

Cleanup

InputTextMultiline() can clip + BeginChildFrame() returns bool. (#200)

Demo for InputTextMultiline() (#200)

Demo for InputTextMultiline() (#200)

InputText(): shallow tweaks (#200)

InputTextMultiline() fixes, vertical scrolling, optimizations (#200) ...

Using a child window for multi-line text.

Increased key repeat rate for non-character input key repeat. ...

Dodgy - we should have a match here for character input and
non-character input (e.g. holding 'a' vs holding 'backspace' should be
same rate), but for the earlier we don't have the info?

InputText: doesn't reset scrolling when active text input becomes bigger than its content. (#200) ...

Mostly because it's expensive.

InputTextMultiline(): vertical scrolling wip, selection rendering fix (#200)

InputTextMultiline(): multi-line selection draw fix (#200)

InputTextMultiline(): multi-line selection draw fix (#200)

InputText() fixing cancel (#200)

InputText() lifted 1024 characters limit (#200) ...

Bit messy & not happy with using ImVector<char>

InputText() fixed multi-line selection clipping. (#200)

InputTextMultiline() tabbing to a multi-line edit doesn't select all (unless ImGuiInputTextFlags_AutoSelectAll is set), somehow arbitrary (# ...

Seems reasonable

InputText: multi-line selection, better scrolling, cleaning up (#200) ...

Not horizontally scrolling on char boundaries anymore

ImFont::RenderText() additional early out (typically performed at TextUnformatted() level for large chunks but this is also useful) (#200)

Merge remote-tracking branch 'origin' into 2015-06-multiline_textedit ...

Conflicts:
	imgui.h

Text rendering can be finely clipped cpu-side on top and left axises (for #200)

Merge remote-tracking branch 'origin' into 2015-06-multiline_textedit ...

Conflicts:
	imgui.cpp