add a dummy T_NUM type
handle the T_NUM coercion (a trivial coercion for all numeric types)
handle T_INT and T_NUM
abs and sgn
only valid complex coercions are to complex, string, num, and cons
revise the string and complex conversions
have 'int and 'num be distinct synthetic types
add arc_expt and T_INT type
add tests for converting strings into integers and floating point numbers
prototypes for __arc_neg and string to flo/int functions
coercions to 'int and 'num
coercions to 'num and 'int, and coercion tests to 'string
perform rounding on coercion of flonums
some tests for int/num conversions
string -> int/num tested