FMSLogo Code

Translate the documentation for data structure predicates into Spanish.
The translation was based on Rosario Ruiz's translation of the MSWLogo manual.

Remove trailing whitespace

Use wxConvISO8859_1 instead of wxConvLib because wxConvLib, in my
Fedora 25 environment failed for any strings which contained non-ASCII
characters. This made it difficult to test the Spanish version on
Fedora 25, which is where I porting the manual into Spanish.

Using wxConvISO8859_1 may prevent other languages from working, but
they probably wouldn't work anyway and the real solution is to
never convert back and forth between char * and wxString (that is,
to truely support Unicode internally).

Combine the examples of PUSH, POP, QUEUE, and DEQUEUE into a single
<programlisting> because the snippets depend on each other and are not
independent listings.

Also add commands to show the stack/queue for POP and DEQUEUE so that
the side-effect of removing an item from the variable is manifest in
the example.

Translate the documentation for the data structure mutators into Spanish.
This was based on Rosario Ruiz's translation of the MSWLogo manual.

Translate the documentation for all data structure selectors into Spanish.
The translation was based on Rosario Ruiz's translation of the MSWLogo manual.

Finish translating the data structure constructors to Spanish.
This translation was based on the translation of the MSWLogo
manual by Rosario Ruiz.

Further note that the predicate input may be an explicit slot template.

Clarify the meaning of the predicate input to SORT.

Explicitly document the origin input.
This inadvertantly removed when the MSWLogo manual was ported
from winhelp to DocBook.