Strlit labels were emitted as `_S_<n>` from a global counter with no
per-unit prefix (cgen.c intern_strlit + wwstage internstrlit twin).
Under separate compilation two str-bearing packages both emit `_S_0`..
-> w6l link collision.
Prefix the label with the owning package PATH (`<module>._S_<n>`,
matching mklabel's spelling). The prefix is c->cur_mod, set per-fn by
cgfn and now per-decl by let_pre_intern (save/restore so the later
emit passes, which read cur_mod for fn-ptr relocs, are unaffected).
Pure function of the module path — NOT a build-nonce — so the
self-host fixed-point holds across ww2/ww3/ww4. Both stages, symmetric.
Transparent rename on the live combined path: the label is interned
once and shared by every reference, so ref and def move in lockstep.
cs==ww byte-id holds; the w6c/wwdump combined.ww embed wcc/cgen.ww and
are regenerated.
746_strdef_inline: the strdef-inline sentinel pinned the bare
`LEAQ\t_S_` shape; update to the module-prefixed form (alpha._S_ for
the in-module def, beta._S_ for the use-site-interned cross-module
inline).
989_m3sep_run: add the #49 LINK leg. The str sub-fixture (sleaf+smid)
was keystone-only — never linked — precisely because the global
counter made both emit `_S_0`. With the prefix, compile both `-c`
separately, link (w6l) + run (sroot reads a distinguishing byte through
each string's .ptr, so a collided label would corrupt the exit), both
stages + cs==ww final exe.