gcc9 warning

[mgerhardy]

/libturbobadger/tb/tb_value.cpp: In member function ‘void tb::TBValue::Copy(const tb::TBValue&)’:
/libturbobadger/tb/tb_value.cpp:208:46: warning: ‘void* memcpy(void*, const void*, size_t)’ writing to an object of type ‘class tb::TBValue’ with no trivial copy-assignment; use copy-assignment or copy-initialization instead [-Wclass-memaccess]
   memcpy(this, &source_value, sizeof(TBValue));