FMSLogo Code

Update Spanish translation table based on recent changes.
This includes an update for Bug #511, which fixed the Spanish translations for
READPOS and WRITEPOS (as POSLECTURA and POSESCRITURA, respectively).

Remove misinformation from PORTMODE documentation
The documentation had conflicting statements that speed could and
could not be set by FMSLogo. In fact, only the flow control cannot
be set through FMSLogo. The misinformation was a transcription error
from porting the MSWLogo RTF documentation to FMSLogo's DocBook format.

Clarify what is meant by "flush" and document that the input is ignored.

Clarify the example's explanatory note.

Remove unneeded parts of the example for ERASEFILE.
All the example wants to show is that a file exists and can be opened.
It's not important to read its contents.

Add missing index for EOF?
This enables selecting EOF? and pressing F1 to jump to the correct documentation.

Translate the documentation for the file I/O commands into Spanish.

Improve the DRIBBLE/NODRIBBLE documentation
1) Add cross-referencing
2) Note that the example must be run line-by-line
(otherwise the dribble file is closed before it logs instructions)
3) Change the first sentence of DRIBBLE to match the style of the
rest of the manual (not "This command does X", but "Does X")

Clarify that setting passing binmode as TRUE will affect both reading and writing.

Add a link to DRIBBLE, in case "the dribble file" is not self-evident.