using bool in rtl::OUStringBuffer::append

[Markus Mohrhard]

Hey,

after I got tinderbox mail complaining about ambiguous overload for
rtl::OUStringBuffer::append(bool) I wanted to ask if we could add a
rtl::OUStringBuffer::append(bool) method or if there are reasons
against it. From what I can see it could in the end even share the
implementation with the sal_Bool variant just needs an own method in
rtl::OUStringBuffer.

Regards,
Markus