A function that gets the index of a picture in a picture table
given its filename. Since we are going to identify pictures by
their filename, we will need this function in the undo code.
Use the function in the remove_picture() function.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
For consistency with equipment, use our table macros for pictures.
Generally tables (arrays) are preferred over linked lists, because
they allow random access.
This is mostly copy & paste of the equipment code.
Sadly, our table macros are quite messy and need some revamping.
Therefore, the resulting code is likewise somewhat messy.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
