BLD: resolve missing prototype warnings in lsoda/vode

[thalassemia]

This resolves a compiler-specific warning that I encountered at some point during my testing with either MSVC or the Intel compilers (don't remember which).

[rgommers]

LGTM, thanks @thalassemia!

With Clang on macOS these warnings were visible too, and are indeed resolved now:

[9/12] Compiling C object scipy/integrate/_lsoda.cpython-310-darwin.so.p/meson-generated_..__lsodamodule.c.o
scipy/integrate/_lsodamodule.c:1045:29: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
                (*f2py_func)(cb_f_in_lsoda__user__routines,&neq,y,&t,&tout,&itol,rtol,atol,&itask,&istate,&iopt,rwork,&lrw,iwork,&liw,cb_jac_in_lsoda__user__routines,&jt) ;
                            ^
1 warning generated.
[11/12] Compiling C object scipy/integrate/_vode.cpython-310-darwin.so.p/meson-generated_..__vodemodule.c.o
scipy/integrate/_vodemodule.c:1452:29: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
                (*f2py_func)(cb_f_in_dvode__user__routines,&neq,y,&t,&tout,&itol,rtol,atol,&itask,&istate,&iopt,rwork,&lrw,iwork,&liw,cb_jac_in_dvode__user__routines,&mf,&rpar,&ipar) ;
                            ^
scipy/integrate/_vodemodule.c:1810:29: warning: passing arguments to a function without a prototype is deprecated in all versions of C and is not supported in C2x [-Wdeprecated-non-prototype]
                (*f2py_func)(cb_f_in_zvode__user__routines,&neq,y,&t,&tout,&itol,rtol,atol,&itask,&istate,&iopt,zwork,&lzw,rwork,&lrw,iwork,&liw,cb_jac_in_zvode__user__routines,&mf,&rpar,&ipar) ;
                            ^
2 warnings generated.