tccasm: Unify C and asm symbol table

This makes the asm symbols use the same members as the C symbols
for global decls, e.g. using the ELF symbol to hold offset and
section.  That allows us to use only one symbol table for C and
asm symbols and to get rid of hacks to synch between them.

We still need some special handling for symbols that come purely
from asm sources.

tccpp.c

@@ -432,7 +432,6 @@ static TokenSym *tok_alloc_new(TokenSym **pts, const char *str, int len)
     ts->sym_label = NULL;
     ts->sym_struct = NULL;
     ts->sym_identifier = NULL;
-    ts->sym_asm_label = NULL;
     ts->len = len;
     ts->hash_next = NULL;
     memcpy(ts->str, str, len);