Replace every use of GNU Patch by the OCaml patch library #4131

Job	Run time
Analyse	34s
Cygwin	5s
Hygiene	58s
Build-Linux (4.08.1)	42s
Build-macOS (4.14.2)	1m 24s
Test-macOS (4.14.2)	2m 12s
Build-Linux (4.09.1)	49s
Build-macOS (5.3.0)	1m 33s
Test-macOS (5.3.0)	2m 21s
Build-Linux (4.10.2)	45s
Build-Linux (4.11.2)	52s
Build-Linux (4.12.1)	45s
Build-Linux (4.13.1)	53s
Build-Linux (5.0.0)	55s
Build-Linux (5.1.1)	46s
Build-Linux (5.2.1)	43s
Build-Linux (4.14.2)	50s
Build-Linux (5.3.0)	49s
Build-Windows (x86_64-pc-cygwin, x86_64-pc-cygwin, 4.14.2)	9m 46s
Build-Windows (i686-w64-mingw32, x86_64-pc-cygwin, 4.14.2)	7m 16s
Build-Windows (x86_64-w64-mingw32, x86_64-pc-cygwin, 4.14.2)	7m 35s
Build-Windows (i686-pc-windows, x86_64-pc-cygwin, 4.14.2)	7m 56s
Build-Windows (x86_64-pc-windows, x86_64-pc-cygwin, 4.14.2)	8m 50s
Build-Windows (x86_64-w64-mingw32, x86_64-pc-cygwin, 5.3.0)	8m 47s
Build-Windows (x86_64-pc-windows, x86_64-pc-cygwin, 5.3.0)	9m 4s
Test-Linux	0s
Cold-Linux	0s
Doc-Linux	0s
Solvers-Linux	0s
Upgrade-Linux	0s
Solvers-macOS	0s
Upgrade-macOS	0s
	1h 17m 10s

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