Update to 0.0.24:

Bump version in view of a possible release
When cached fg and bg colours are 0, trust index more
coverity: copying uninitialized value
coverity: do not let VisioDocument::parse throw
coverity: drop duplicated code
coverity: consistently check ret. value of read*Data
Trying to support initially Text Fields
Fixed line height is in inches :(

(wiz)