Provide typedef names of anonymous structs/unions where appropriate

[hainest]

typedef struct { int x; } Foo;
void foo(Foo f) {}

Smeagle produces

{
 "library": "libtest.so",
 "locations":
 [
   {
    "function": {
      "name": "_Z3foo3Foo",
      "parameters": [
        {
          "name":"f",
          "type":"{anonymous struct at /home/tim/workspace/Smeagle/abi-examples/test.cpp:19}",
          "class":"Struct",
          "location":"%rdi",
          "direction":"import",
          "size":"4",
          "fields": [
           {
             "name":"x",
             "type":"int",
             "class":"Scalar",
             "size":"4"
           }]
        }
    ]
   }}
]
}

We should try to check if a struct/union is anonymous and, where possible, assign its type name as the name of the typedef. Not all anonymous structs/unions are created via a typedef, so they may just have no name at all.