RT support 4 C: Fixed ambiguous comma in buffer.h

In the buffer reference counter decrmenetation, ambiguous
comma started to produce compiler error (code without effect).
Parentheses added to avoid confusion and increase readability.
RT support 4 C: silent building
Added timer implementation

src/CXX/sys was created to hold classes representing system resources.
The 1st one is a timer implementation (using monotonic clock).
Documentation: Developer's guide in PDF added

Developer's guide is now being also built and distributed in PDF.