verible-verilog-obfuscate crashes when program has pragma directive

[rafasumi]

When you try to obfuscate SystemVerilog code with the `pragma protect directive, the obfuscator crashes because decoding the obfuscated code doesn't match the original code. For instance, take this example:

`pragma protect begin_protected
`pragma protect key_keyowner = "Cyberdyne Technologies", key_keyname = "cdn_rsa_key", key_method = "rsa"
`pragma protect end_protected

If you try to use it with verible-verilog-obfuscate without any additional options, it crashes with the following output:

Internal error: decode(encode) != original
ORIGINAL:
`pragma protect begin_protected
`pragma protect key_keyowner = "Cyberdyne Technologies", key_keyname = "cdn_rsa_key", key_method = "rsa"
`pragma protect end_protected

ENCODED:


DECODED:


*** Please file a bug. ***

I'm not sure what is the expected behavior for this example. The parser apparently ignores the rest of the line whenever there is a `pragma. However, I believe the obfuscator isn't expected to crash in cases like this.