Remove unused classes and methods

Removed Bitmap and MinikinFontFreeType classes, as well
as the Layout::draw() method.

The code was there for debugging purposes and for potential
third-party users. We no longer support third-party uses of
Minikin, since we don't know of any.

Test: mmma -j frameworks/minikin builds with no errors
Change-Id: Iddc9e8d35334053bd5255bccf3dbe5ba1eecf814

• include/minikin/Layout.h[diff]
• include/minikin/MinikinFont.h[diff]
• include/minikin/MinikinFontFreeType.h[Deleted - diff]
• libs/minikin/Android.mk[diff]
• libs/minikin/Layout.cpp[diff]
• libs/minikin/MinikinFontFreeType.cpp[Deleted - diff]
• tests/unittest/Android.mk[diff]