Work on copy_extended_sym to properly copy struct members.

I'm still getting errors, but this is a good pause point that includes
quite a bit of code working towards a solution.
Fields appear to be correctly sym_push-ed
Found malformed linked list in copy_extended_sym
Realized linked list was not malformed
Found lingering extended token bit
Fixed lingering extended token bit
Removed debugging printfs
Cleaned up recent work on copy_extended_sym
Cleanup Makefile for better automated testing
Started work on test 35
Fix stack overflow due to infinite recursion
Make extended symbol copying aware of tok ids being SYM_FIELD

Parts of tcc push anonymous symbols with token ids of SYM_FIELD.
These anonymous symbols are usually pointers to other symbols or
the head of function prototype lists.
Fix failed bit masking in copy_ctype
Update makefile for next test; note test 40 passed without trouble!
Get test 42 to pass by with local stack and copy_extended_tokensym fixup

The machinery kicked off by copy_extended_tokensym makes quite a
bit of use of sym_push. The problem that test 42 revealed is that
the symbol that is needed happens to be called for the first time
in a block (which I expect will be the case most of the time),
then local_stack will be defined, and sym_push will push to that
location. Then, during the end-of-scope stack popping, the values
get reset! To fix this, I simply created a way to temporarily
turn the local stack, and later restore it.
Minor cleanups to test 42
Move to test 45
Test 45 passes
Got test 20 working again
47 passes