llvm-dg-dump: add -mark option
llvm-dg-dump: add -mark option

This option works the same as -slice but does not
slice away the nodes, just marks them

Signed-off-by: Marek Chalupa <a05df156a69ad59faa9af9b666ef78009594c145@gmail.com>

mchalupa/dg,mchalupa/dg,mchalupa/dg,mchalupa/dg