asmfmt incorrectly alters quoted strings

With the following example, I would expect no change after running asmfmt:
```asm
db ","
db ";"
db "http://example.com"
db ','
db ';'
```

Currently I get the following output, with spaces added erroneously:
```asm
db ", "
db "; "
db "http: // example.com"
db ', '
db '; '
```

I'm keen to make a PR for this.