Implement clang-based scanner

[ChiefGokhlayeh]

As discussed in #3 (comment), explore possibilities of using libclang's C API. Fortunately, libclang provides Python bindings for their C API.

Experimenting with it demonstrated, that libclang provides deeper lexical fidelity when parsing a C source/header file (i.e. it provides preprocessor tokens before they're expanded). Perhaps this can be used to more effectively work around __asm__(...)-statements, which make direct inclusion of that particular file impossible.

[ChiefGokhlayeh]

On the topic of "impossible headers":

Assume the following header:

#ifndef DRIVER_H_
#define DRIVER_H_

void some_func(void)
{
    __asm__("bkpt");
}

#endif DRIVER_H_

Not that some_func is defined directly within the header file. Note also that __asm__("bkpt"); is not a valid x86(_64) instruction. The compiler will therefore refuse compilation, even if some_func is cleverly knocked out through the workaround stated in In-Header Defined Functions.

The only solution I see is to abandon the "wrapping" philosophy and resort to "banning" the original header. Utilizing libclangs deeper lexical offerings we might be able to "copy" a slimmed down version of the original header and kick out such in-header definitions, while keeping declarations and inclusions intact.

Unfortunately, the same can not be done for illegal instructions inside C macros. Without expanding such a macro in the appropriate context, nobody can tell what its contents mean (they could be virtually anything, so reliably parsing it is effectively impossible). Some more thinking required...