Plug some memory leaks.

Plug some memory leaks.

The optimizer and code emitter (icode_to_fcode()) allocate their own
memory that must be cleaned up if an error is thrown, so we can't use
bpf_error(), we need to add our own error routines for them.

In some cases, just free up the memory before calling bpf_error().

Credit to OSS-Fuzz for finding this issue.