wasm2c no longer passes many spec tests

[sbc100]

Many test fail because the recent spec tests now require multi-table and reference-type support. I was forced to delete the following tests for that reason:

• test/wasm2c/spec/br_table.txt
• test/wasm2c/spec/call_indirect.txt
• test/wasm2c/spec/elem.txt
• test/wasm2c/spec/exports.txt
• test/wasm2c/spec/imports.txt
• test/wasm2c/spec/table.txt
• test/wasm2c/spec/linking.txt
• test/wasm2c/spec/select.txt

The new version of test/wasm2c/spec/data.txt fails because somehow the bounds checks don't seem to work for zero-sized memories. This test tails to trap:

(assert_trap                                                                        
  (module                                                                              
    (memory 0)                                                                   
    (data (i32.const 1))                                                         
  )                                                                              
  "out of bounds memory access"                                                  
)