Errors and error handling

These are the declarations used by the error handling:

   int errno;
   int complex_error(int, double);

cosh(zz):
C_COSH_RE	|zz.re| too large. Value with correct angle and huge magnitude returned.
C_COSH_IM	|zz.im| too large. Complex(0,0) returned.
exp(zz):
C_EXP_RE_POS	zz.im too small. Value with correct angle and huge magnitude returned.
C_EXP_RE_NEG	zz.re too small. Complex(0,0) returned.
C_EXP_IM	|zz.im| too large. Complex(0,0) returned.
log(zz):
C_LOG_0	zz==0. Value with a large real part and zero imaginary part returned.
sinh(zz):
C_SINH_RE	|zz.re| too large. Value with correct angle and huge magnitude returned.
C_SINH_IM	|zz.im| too large. Complex(0,0) returned.

None of the functions will throw an exception directly, but it is possible that a user-provided complex_error may throw an exception. Accordingly, those functions that might result in an error condition have no exception specification, while all other functions have an empty exception specification.