BPFProgTable: allow to remove elements

It is allowed in the kernel from some time ago:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/bpf/arraymap.c?h=v4.4#n267Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>

src/cc/api/BPFTable.h

@@ -287,6 +287,12 @@ public:
       return StatusTuple(-1, "Error updating value: %s", std::strerror(errno));
     return StatusTuple(0);
   }
+
+  StatusTuple remove_value(const int& index) {
+    if (!this->remove(const_cast<int*>(&index)))
+      return StatusTuple(-1, "Error removing value: %s", std::strerror(errno));
+    return StatusTuple(0);
+  }
 };
 
 }  // namespace ebpf