fix Issue 12855 - Shadow register assignments for spilling can conflict
fix Issue 12677 - Assertion failure: 'isCtfeValueValid(newval)' on line 6579 in file 'interpret.c'
Merge pull request #3649 from 9rnsr/fix12677

Issue 12677 - Assertion failure: 'isCtfeValueValid(newval)' on line 6579 in file 'interpret.c'
Merge pull request #3622 from WalterBright/fix12855

fix Issue 12855 - Shadow register assignments for spilling can conflict