Fixed a number of problems revealed by bug #827883.

Fixed a number of problems revealed by bug #827883.
* src/SDCCloop.c (loopInvariants): Spill location of the
result operand should be recomputed if extracted from
a loop. Also, don't extract assignments of an iTemp
from a literal.
* src/SDCCast.c (isConformingBody): loop reversal should
not occur if the control variable is involved with a
relational operator.

git-svn-id: https://sdcc.svn.sourceforge.net/svnroot/sdcc/trunk/sdcc@2967 4a8a32a2-be11-0410-ad9d-d568d2c75423