Stub generation doesn't handle 'protected' multi-line String correctly.

When using the groovyc joint compilation feature, the generated stub is incorrect when the groovy source includes a protected (possibly affects public too, I didn't test) multi-line String 'constant'.

For example,

class Example {
protected static final String CONSTANT_VALUE = """
I am a constant value
Thank you
"""
}

would generate a stub:

public Example extends java.lang.Object implements groovy.lang.GroovyObject {
protected static final java.lang.String CONSTANT_VALUE = "
I am a constant value
Thank you
";
}

This is a syntactically incorrect Java statement.