Rename "modulo" to "remainder"

[cousteaulecommandant]

When negative numbers are involved, "modulo" typically refers to an operation that has the same sign as the second operand, whereas "remainder" has the sign of the first (this distinction is clear e.g. in the Ada language, which has both mod and rem operators). Specifically, the standard refers to the result of % as "remainder", not "modulo".
In Python, for example, (-11) % 10 is 9, but in C and C++ it is -1). This can be a problem if % is being used to restrict an array index to a range (e.g. to implement a circular buffer), if said index can be negative.

I have replaced all occurrences of "modulo" with "remainder" in modulo.adoc, and provided two examples of what happens when you use % with negative operands. However I have left the file name as "modulo.adoc" (because honestly I have no idea what happens if you mess with the file names).

[SimonePDA]

I have to ask to the team if they agree on this change.

[Artoria2e5]

An argument for this terminology can be that it is consistent with C/C++ standard (http://port70.net/~nsz/c) descriptions, but conversely it should be noted that C++11 calls it "modulus" too. Nevertheless "remainder" wins out at accuracy and familiarity.

[cousteaulecommandant]

Should the file be renamed to remainder.adoc? Now it's everything fine except that the top of the documentation still says "Reference > Language > Structure > Arithmetic operators > Modulo" (I don't know if just changing the file name fixes this; I assumed the title_expanded: field would take care of this.)

[SimonePDA]

I took care of that change. Thank you for pointing that out.

[cousteaulecommandant]

It would seem that remainder.adoc was successfully created, but the commit that removes modulo.adoc failed to build; as a result, there are now two entries for "% (remainder)" in https://www.arduino.cc/reference/en/

[SimonePDA]

Yes, I know. It is a bug about deletions. We will take care of it after this holidays.