[CM] S7 integrated in TIC-80, and bug reports

[bil at ccrma.Stanford.EDU]

I don't think standard scheme allows set! with a target that is a pair,
or at least I can't find anything about it in r7rs.pdf.  In s7,
the target needs a setter.

The jmp_bufs are needed to unwind the C stack if an error is raised.
It might work to make longjmp a no-op -- the stack will grow as
each error is hit, but s7 might keep chugging along until you get
a stack overflow.

Does Android have the other complex math functions?  If so, I could
add ifdefs along the lines of the existing FreeBSD cases to add those
two functions in Android.