add examples/txtest.c
stylequad: load texture from background-image property
stylequad no longer inherits from rtb_quad
first crack at texture borders
add texture for text input
stylequad: draw border inside texture
revised focus button
get min-width and min-height from stylesheet
Merge branch 'stylequad-textures'

this branch was for adding the necessary plumbing for finally providing
automatic texturing of widgets based on properties specified in the CSS.