Remove most calls to fixup_symbol_section

Nearly every call to fixup_symbol_section in gdb is incorrect, and if
any such call has an effect, it's purely by happenstance.

fixup_section has a long comment explaining that the call should only
be made before runtime section offsets are applied.  And, the loop in
this code (the fallback loop -- the minsym lookup code is "ok") is
careful to remove these offsets before comparing addresses.

However, aside from a single call in dwarf2/read.c, every call in gdb
is actually done after section offsets have been applied.  So, these
calls are incorrect.

Now, these calls could be made when the symbol is created.  I
considered this approach, but I reasoned that the code has been this
way for many years, seemingly without ill effect.  So, instead I chose
to simply remove the offending calls.

gdb/objfiles.c

@@ -582,8 +582,6 @@ static void
 relocate_one_symbol (struct symbol *sym, struct objfile *objfile,
 		     const section_offsets &delta)
 {
-  fixup_symbol_section (sym, objfile);
-
   /* The RS6000 code from which this was taken skipped
      any symbols in STRUCT_DOMAIN or UNDEF_DOMAIN.
      But I'm leaving out that test, on the theory that