release 1.80

• added 'downto' range expression to make the step -1 common case easier
• reverse(float array) now works
• fixed some compiler problems related to the data type of array literals
• reintroduced alternative string encoding via @"...." syntax (for c64 this is the screencode encoding, rather than petscii which is the default for strings)
• introduced romsub keyword, to define ROM subroutines, instead of using asmsub
• compiler speed improved (callgraph logic was improved)
• floating point assembly code moved to separate embedded library file