In the definition of the terminals in section "A. IDL grammar" you'll find the following definition of the whitespace terminal:

whitespace = [\t\n\r ]+|[\t\n\r ]*((//.*|/\*.*?\*/)[\t\n\r ]*)+

Let's look at its part specific to block comments ("/* ... */"):

/\*.*?\*/

What does this regular expression look for (see the referenced document http://search.cpan.org/dist/perl/pod/perlre.pod for details):

a string '/*'
followed by 0 or more "any character (except newline)", not greedily (the latter one follows by using '*?' instead of '*')
followed by the string '*/'.

What consequence does this have? The answer is that block comments can't contain newline characters between the block comment delimiters - I don't believe this is what you intend.

Thus I believe, the regular expression has to be fixed. I propose the following fix, but better check it thrice for correctness:

We change the part

/\*.*?\*/
to
/\*[.\n]*?\*/

Thus the complete definition of the whitespace terminal changes to
whitespace = [\t\n\r ]+|[\t\n\r ]*((//.*|/\*[.\n]*?\*/)[\t\n\r ]*)+