Changes compared to version 2.5

o  Only evaluate TO and STEP expressions once
o  Evaluate TO expression before evaluating the loop assignment
o  Fixed times() to have an argument for portability.
o  Check for log2 for not depending on C99
o  Check more gcc warnings being supported
o  Fixed various warnings
o  INC/DEC/INPUT/READ of local variable works
o  Prefer gettimeofday() over times() for TIME implementation
o  Accept "pr" as another shortcut for "print"
o  Added option -d to convert DO to REPEAT
o  Added rnd(a,b) for a range
o  Added commandcount()
o  Use setenv instead of putenv
o  Check MID$ assignment overrun
o  Add optional status to SYSTEM
o  Keep first #! line when saving a program
o  INPUT from closed channel fixed
o  ON ERROR no longer catches terminal interrupt
o  A relative program file name is converted to an absolute pathname
   for SAVE without arguments saving it back to the original file.
o  FNEND explained in manual
