Some functions are returning uninitialized values (sometimes silently!) when `ierr /= 0` internally

These functions return uninitialized values when `ierr /= 0` internally. In some cases, they return the value silently and the simulation continues to run!

```
adipls/adipack.c/adipls/signew.n.d.f
double precision function signew(

num/private/mod_brent.f90
real(dp) function eval_brent_safe_zero(

num/private/mod_dopri5.f
real(dp) function hinit(

num/private/mod_dop853.f
function hinit(

interp_2d/private/renka790_sg.f
double precision FUNCTION do_CS2VAL_db (
real FUNCTION do_CS2VAL_sg (

net/public/net_def.f90
integer function get_net_timing_total(

star/private/star_utils.f90
real(dp) function get_tau_at_r(

star/private/rsp_build.f90
real(dp) function eval_T_residual(

astero/private/astero_support.f90
real(dp) function get_chi2(

astero/private/extras_support.f90
integer function astero_how_many_extra_history_columns(
integer function astero_extras_finish_step(
integer function astero_extras_check_model(

astero/private/astero_run_support.f90
real(dp) function eval1(

binary/private/binary_history.f90
integer function how_many_binary_history_columns(

binary/private/binary_mdot.f90
integer function check_implicit_rlo(

binary/public/binary_lib.f90
real(dp) function binary_compute_k_div_T(
```