posix: remove pmemfile_dup*

[mslusarz]

dup/dup2 is implemented on libpmemfile.so side without any help from libpmemfile-posix.so.

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This change is 

[codecov[bot]]

Codecov Report

Merging #342 into master will increase coverage by 0.08%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #342      +/-   ##
==========================================
+ Coverage   73.66%   73.74%   +0.08%     
==========================================
  Files          64       64              
  Lines        7990     7984       -6     
  Branches     1613     1613              
==========================================
+ Hits         5886     5888       +2     
+ Misses       1588     1581       -7     
+ Partials      516      515       -1

Flag	Coverage Δ
#sqlite_tests	45.65% <ø> (+0.04%)	:arrow_up:
#tests_antool	12.22% <ø> (ø)	:arrow_up:
#tests_posix_multi_threaded	26.01% <ø> (+0.09%)	:arrow_up:
#tests_posix_single_threaded	56.09% <ø> (+0.05%)	:arrow_up:
#tests_preload	45.52% <ø> (+0.08%)	:arrow_up:

Impacted Files	Coverage Δ
src/libpmemfile/libpmemfile-posix-wrappers.h	53.48% <ø> (ø)	:arrow_up:
src/libpmemfile-posix/file.c	70.94% <ø> (+1.16%)	:arrow_up:
src/libpmemfile-posix/dir.c	85.01% <0%> (+0.24%)	:arrow_up:
src/libpmemfile-posix/rename.c	92% <0%> (+0.4%)	:arrow_up:

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[krzycz]

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Reviewed 4 of 4 files at r1. Review status: all files reviewed at latest revision, all discussions resolved.

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Comments from Reviewable

[sarahjelinek]

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Review status: :shipit: all files reviewed at latest revision, all discussions resolved, all commit checks successful.

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Comments from Reviewable