Test suite fixes

We are almost there. Only a couple of tests still fail (at least on linux X86_64):

1. runnable/xtest46.d. 
See D-Programming-Language/dmd#3729 

2. compilable/cppmangle.d. 
    ```
    struct S1;
    void f(S1 s);
    ```
Because the size of `s` is unknown, LDC fails when trying to decide whether it is passed in a register or the stack.

3. fail_compilation/fail152 and fail_compilation/fail274.
LDC has its own asm parser, hence it outputs different error messages.

4. compilable/ice11925.
LDC does not permit to goto into try, volatile or synchronized statements. Can and should this be implemented?

5. fail_compilation/fail8179b. 
Unlike dmd, ldc allows casting from T[] to T[x][1]. Should it be forbidden?