[patch] bug 15055 Add Unistd.h to OProfileWrapper.cpp

Add #include <unistd.h> to OProfileWrapper.cpp.   This provides the declarations for 'read' and 'close' that are otherwise missing, and result in 'error: <foo> was not declared in this scope'.

This matches the issue as reported in bug 15055 "Can no longer compile LLVM with --with-oprofile"