Asciidoxy treats cmake source code as though it was asciidoxy directives

[mkschreder]

The following code generates error:

[source,cmake]
----
some_cmake_code(${CMAKE_VARIABLE})
----

ERROR: Error while processing AsciiDoc files:
Undefined
Traceback:
  File index.adoc, line 16, in AsciiDoc
    ${include("document.adoc", leveloffset="+1")}
  File document.adoc, line 7, in AsciiDoc
    ${include("document.adoc")}
  File document.adoc, line 96, in AsciiDoc
    some_cmake_stuff(${CMAKE_VARIABLE}) <- this is problematic

Asciidoxy also seems to ignore asciidoc comments where even lines prefixed with "//" are still processed.

This is a bug since:

1. source blocks must not be treated as asciidoxy code
2. Comment blocks must not be expanded as asciidoxy directives