Restrict Checks for Open/Mapped Files

While checkpointing (Dumping), CRIU stores some meta-information about the open/mmaped file and this is validated while restoring to make sure that the right file is being restored. Currently, the only meta-information stored is the file size. The goal of this project is to extend this meta-information to include other information so that the possibility of an incorrect restore is reduced. Two more types of validation will be present, in addition to the File Size validation, after the completion of this project - Build-ID Validation and Checksum Validation. The implementation must also be tested using the ZDTM test suite.