ecl: create-image: don't call internal function compute-init-name
It is wrong to call this function. If :init-name is not supplied, or NIL ECL will compute the init name itself (it is not a new mechanism).
Enabling specifying init-name makes it possible to build static and shared libraries with known initialization function (important, when CL module is linked with bigger C/C++ project outside ASDF).
If :init-name is NIL, it will default to compute-init-name internally. Calling explicitly is not guaranteed to work in the future (internal mechanism).