Currently we rely on detecting the source language of a class by the
name of the symbol pointing to it. This generally works, but there are
scenarios where Swift generates both an ObjC name and a Swift name for
the symbol - by aliasing the ObjC name to the Swift name, as follows:
```
.globl _OBJC_CLASS_$__TtC11MyTestClass11MyTestClass
.private_extern _OBJC_CLASS_$__TtC11MyTestClass11MyTestClass
.set _OBJC_CLASS_$__TtC11MyTestClass11MyTestClass, _$s11MyTestClassAACN
```
So to correctly detect the source language in all cases, we need to
handle scenarios where both an ObjC symbol and a Swift symbol is defined
for a class - in this case the symbol is always a Swift class.
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