Maintain an explicit "reachable" flag when decoding wasm. Push placeholder
frames on the control-flow stack instead of just maintaining a count of
the stack depth in unreachable code, so that we can whether If blocks
have Elses, and whether block exits are branched to, in all contexts.
Fixes#217.
* wasm testsuite: ignore hidden files in test dir
and report a rejected file. it was picking up vim .swp files
* wasmtests: correct wat syntax in icall.wat
The function environment is now expected to keep track of the function
signatures in the module, and it is asked to generate Cretonne
signatures to be used for indirect calls.
The combination of make_indirect_sig() and translate_call_indirect()
callbacks allow the runtime to insert additional function arguments for
indirect calls such as vmctx pointers and CFI-style signature identifiers.
