FMSLogo Code

Reorganize the content of SETTURTLEMODE to improve clarity.

Clarify that TURTLE outputs a number, not a turtle.

Clarify the final sentence of the description of SETTURTLE, which describes when a turtle gets the shared pen.
Also clarify the examples a little.

Translate the front-matter for the Graphics chapter to Spanish.
This translation is based on Rosario Ruiz's translation of the MSWLogo manual.

Update the polygon demo to use multiple colors when drawing the sphere.
This demonstrates the feature that each surface can have a different color, which is something that I had forgotten FMSLogo supported. Putting this into DEMO makes it more discoverable.

Fixes to the polygon section
* Clarify that POLYEND does not display the polygon.
* Clarify how POLYVIEW shows colors where FILL doesn't.
* Fix broken example code under Restriction #1.

Fix a bug on Fedora Core 27 where RANDOM could output a negative number.
Apparently, the code did not expect RAND_MAX to ever be larger than 2**15.
Also remove the defunct "#ifdef bsd" blocks, since these will never be used again in FMSLogo.

Test that RANDOM can output number greater than 16 bits.
There is special logic in lrandom() to be able to do this.
Also make minor updates to the test style, using procedures which
didn't exist when the test was originally written.

Implement TIMEMILLI on GNU/Linux.
This was needed to be able to run RANDOMTEST, which was needed to
fix a bug in RANDOM where it output negative numbers on Fedora Core 27.

Fix a critical typo "position Y axis" -> "positive Y axis".
The previous wording made no sense for an orientation.