Break up mdbcomp/prim_data.m. The new modules have much better cohesion.

mdbcomp/sym_name.m:
    New module, containing the part of the old prim_data.m that
    dealt with sym_names.

mdbcomp/builtin_modules.m:
    New module, containing the part of the old prim_data.m that
    dealt with builtin modules.

mdbcomp/prim_data.m:
    Remove the things that are now in the two new modules.

mdbcomp/mdbcomp.m:
deep_proiler/Mmakefile:
slice/Mmakefile:
    Add the two new modules.

browser/*.m:
compiler/*.m:
deep_proiler/*.m:
mdbcomp/*.m:
slice/*.m:
    Conform to the above changes.