ARM: handle strings in a function body

Try to handle the following case when `naked` attribute is used to prevent function prologue/epilogue generation, and uses the body for strings:
```c
#include

__attribute__ ((naked)) void my_mum_said_im_special(){
asm ( ".long 0x6C6C6548" );
asm ( ".long 0x6f57206f" );
asm ( ".long 0x00646c72" );
}

int main(){
const char *s = (const char *)&my_mum_said_im_special;
printf( "%s\n", s );
return 0;
}
```

[naked.zip](https://github.com/avast-tl/retdec/files/1700360/naked.zip)

It is from [this article](https://www.evilsocket.net/2015/05/02/using-inline-assembly-and-naked-functions-to-fool-disassemblers/).

Start by reproducing the ARM case from naked.zip and compare RetDec's output for the C sample using naked functions and inline assembly strings. Trace the decompiler's handling of naked function bodies and embedded string data. Done means the sample is handled without losing or misinterpreting the string content.

Written by the indexing model from the issue text.