Register and add among JT reasons FunctionSymbol

The symbol handling has been extended to register whether a symbol
represents a function or not. This information is then used to register,
during the global data harvesting phase, all the function symbols and
explicitly mark them through the "FunctionSymbol" `JTReason`.

We use this information during the CFEP harvesting phase to integrate
the information produced by the function boundaries detection with
potential unidentified CFEPs.

This option can be enabled with the `--use-debug-symbols`, which
supersedes `--use-sections`.

binaryfile.cpp

@@ -385,10 +385,11 @@ void BinaryFile::parseELF(object::ObjectFile *TheBinary,
     // Collect symbol names
     for (auto &Symbol : TheELF.symbols(SymtabShdr)) {
       Symbols.push_back({
-        Symbol.getName(StrtabContent).get(),
-        Symbol.st_value,
-        Symbol.st_size
-      });
+                          Symbol.getName(StrtabContent).get(),
+                          Symbol.st_value,
+                          Symbol.st_size,
+                          Symbol.getType() == ELF::STT_FUNC
+                        });
     }
   }