interlace: Store unsigned integers in unsigned integer types

And add some assertions to guard against overflows and out of bounds
reads.
19 jobs for 1.16 in 60 minutes and 30 seconds (queued for 53 seconds)
Status Job ID Name Coverage
  Preparation
passed #1083003
gst indent

00:00:40

passed #1083002
manifest

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  Build
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build cerbero android universal

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build cerbero cross win32

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build cerbero cross win64

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build cerbero fedora x86_64

00:05:21

passed #1083016
gst-ios-13.2
build cerbero ios universal

00:44:45

passed #1083015
gst-macos-10.15
build cerbero macos x86_64

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build fedora x86_64

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passed #1083010
1809 windows docker
build msys2

00:31:55

passed #1083005
build nodebug fedora x86_64

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passed #1083251
build static fedora x86_64

00:10:57

passed #1083007
build static nodebug fedora x86_64

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passed #1083008
1809 windows docker
build vs2017 amd64

00:09:39

passed #1083009
1809 windows docker
build vs2017 x86

00:10:01

failed #1083006
build static fedora x86_64

00:08:00

 
  Test
passed #1083017
gstreamer
check fedora

00:03:13

passed #1083018
gstreamer
integration testsuites fedora

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  Integrate
passed #1083019
android universal examples

00:09:36