Generate different LOD of orthomgraphic image into one texture

Because of f5cc5d0b403d1e26fd3fbd286ab911724d061a1f, height map
texture introduced in d1779b9543b3e8304a2dd733eb0e329905eacd40 is
no longer used, so it can used to render orthomgraphic image. That
is, the texture is used for Fragment shader instead of
vertex shader.

In this impl, orthomgraphic image must be strip based square tiff
image, and only one row in each strip. And it must start from
integer coordinate and covers 1 second in latitude and longitude.

Signed-off-by: plysan <plysab@gmail.com>
Remove libtiff warnings when opening tiff image files

Signed-off-by: plysan <plysab@gmail.com>