Use CreateMemCpy that takes MaybeAlign in LLVM 10
Use CreateMemCpy that takes MaybeAlign in LLVM 10

This fixes the following warning:

```
/home/ubuntu/work/bpftrace/bpftrace/src/ast/codegen_llvm.cpp:705:8: warning: 'CreateMemCpy' is deprecated: Use the version that takes MaybeAlign instead [-Wdeprecated-declarations]
    b_.CREATE_MEMCPY(b_.CreateGEP(perfdata, {b_.getInt64(0), b_.getInt64(sizeof(uint64_t) + 2 * sizeof(uint64_t))}), str_buf, map.ident.length() + 1, 1);
```

iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace,iovisor/bpftrace