gstinfo: Add new API for getting debug log lines

If you're using a custom log handler, you had to reverse-engineer the
debug log format and create your own format function. Now, you can
call `gst_debug_log_get_line()` and it will return a string (without
ANSI escape color codes) representation instead.

This is useful in situations when you need to log the ordinary
gst_debug log to a resource that can't be opened as a `FILE` handle.
28 jobs for new-api-debug-log in 180 minutes and 8 seconds (queued for 34 seconds)
latest
Status Job ID Name Coverage
  Preparation
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gst indent

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manifest

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  Build
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build cerbero cross-android universal

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manual #650860
gst-ios-12.2 allowed to fail manual
build cerbero cross-ios 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

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gst-macos-10.14
build cerbero macos x86_64

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build clang fedora x86_64

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build fedora x86_64

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docker windows 1607
build msys2

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build nodebug fedora x86_64

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build static fedora x86_64

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build static nodebug fedora x86_64

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docker windows 1607
build vs2017 amd64

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docker windows 1607
build vs2017 x86

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gst-macos-10.14
build cerbero macos x86_64

01:00:00

 
  Test
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check fedora

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integration testsuites fedora

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valgrind bad

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valgrind base

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valgrind core

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valgrind ges

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valgrind good

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valgrind ugly

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  Integrate
passed #650869
cross-android universal examples

00:08:20

manual #650871
gst-ios-12.2 allowed to fail manual
cross-ios universal examples
passed #650870
documentation

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