lib/py: add VMA_AREA_MEMFD constant

[rst0git]

VMA_AREA_MEMFD was introduced with commit 29a1a88bcebaf9d83591077d2bec424da82c0e71. This pull request extends the status map used in CRIT and coredump with the value of this constant to recognise it.

Before:

sudo crit show dump/zdtm/static/maps01/56/1/mm-57.img
...
                {
                    "start": "0x7f224b4d4000",
                    "end": "0x7f224b4d5000",
                    "pgoff": 0,
                    "shmid": 6,
                    "prot": "PROT_READ | PROT_WRITE",
                    "flags": "MAP_SHARED",
                    "status": "VMA_AREA_REGULAR | VMA_FILE_SHARED | 0x4000",
                    "fd": -1,
                    "fdflags": "0x2"
                },

After:

sudo crit show dump/zdtm/static/maps01/56/1/mm-57.img
...
                {
                    "start": "0x7f224b4d4000",
                    "end": "0x7f224b4d5000",
                    "pgoff": 0,
                    "shmid": 6,
                    "prot": "PROT_READ | PROT_WRITE",
                    "flags": "MAP_SHARED",
                    "status": "VMA_AREA_REGULAR | VMA_FILE_SHARED | VMA_AREA_MEMFD",
                    "fd": -1,
                    "fdflags": "0x2"
                },

[codecov-commenter]

Codecov Report

Patch coverage has no change and project coverage change: +0.11% :tada:

Comparison is base (242de4e) 70.55% compared to head (9e62b8d) 70.66%. Report is 2 commits behind head on criu-dev.

:exclamation: Current head 9e62b8d differs from pull request most recent head 6ffb81b. Consider uploading reports for the commit 6ffb81b to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## criu-dev #2245 +/- ## ============================================ + Coverage 70.55% 70.66% +0.11% ============================================ Files 134 133 -1 Lines 33304 33312 +8 ============================================ + Hits 23497 23541 +44 + Misses 9807 9771 -36 ``` [see 11 files with indirect coverage changes](https://app.codecov.io/gh/checkpoint-restore/criu/pull/2245/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=checkpoint-restore)

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