test_tfsat.c: Remove some forward declarations and unused variables.
tfsat.c: Handle embedding a little better.  It was previously not
marking T in the case of T satisfies (T) except E.
scobind/ti_bup/ti_tdn: keep track of conditional context within and
expressions.

This lets stuff like 'flg := R has Field and characteristic$R > 0' go through
algebra: Removed a few instances of 'P pretend X' where X can be inferred
from context.
Merge branch 'master' of https://github.com/pippijn/aldor into pab/devel
algebra: Pretend removal

Most instances of 'R pretend X' where R is a domain replaced with simply R.
Remaining cases are mostly either skipped in the current compile (multpoly),
or "% pretend X", which can still be required (erroneously).