[PATCH, Fortan] fix initialization of flag_errno_math and flag_associative_math

[VandeVondele Joost]

> Why do you want -fno-math-errno to be the default for gfortran?

because it was with rth's commit? This makes sense also because errno is a variable that is defined for C, and not accessible from Fortran. Why would you want -fmath-errno to be the default ?

>  if (flag_associative_math == -1)
>    flag_associative_math = (!flag_trapping_math && !flag_signed_zeros);

> Why this is not working is beyond my understanding, but I am not sure that your fix is the right one.

while the details of the option handling are rather opaque to me to, at the point of reaching this statement, flag_associative_math currently equals 0 or 1 even if the user didn't specify the flag. I believe as set by common_handle_option. With my patch, the value of -1 is seen when the user did not specify the flag explicitly.

Note that the go frontend uses a similar approach for errno.

Joost