Replace calc3() with sqcalc() to unify in-line calculator implementation

Calc3 is an very old one-line calculator module I have created some decades
ago.  I couldn't get rid of it for long time because Squirrel interpreter
has not been able to parse some floating number literal expressions.
Now that we patched Squirrel source to interpret them correctly, we
no longer need to keep 2 separate formula interpreters in stellar
structure definition files.

Compared to calc3(), Squirrel may take some more time to yield an
expression's value since it has more complex syntax and requires
bytecodes to be compiled first, but it would only be required once
at program startup.  The merit of unification of codes would easily
overcome this overhead.

Calc3() is a recursive descent parser which was good for simple
calculation, but we need more versatile parser to treat various
objects.  Specifically, we want to use vectors, quaternions and
matrices in expressions.
Delete calc3 sources since it's no longer used by anyone
Simplify StellarFileLoadInt() invocation

Specifically, removed struct varlist which is remnant of calc3.

Also removed extra allocation of Squirrel tables for local variables
to optimize delegate chain.