Expand a comment explaning common reasons for odd compile errors.

If there is a missmatch between the calling specification in the Invoke
method with the worklet operator, then you get very odd compile errors.
This change expands a comment that tries to explain common reasons for
such errors and things to check.
Merge branch 'compile-error-explanation'
Add copy constructors and operators for array portals

Although it should not be necessary to create copy constructor and equal
opeartors that do a basic ivar copy, we have had problems with the default
versions provided by the compiler. Sometimes they end up very slow for
no particular reason. Also, by providing templated copy constructors, the
array portals can be allow type casting that you would expect.
Merge branch 'array-portal-copy'
Add Worklets.h to list of header files for Mandlebulb benchmark.
Merge branch 'missing-mandlebulb-header'