Log Message:
gtksourceview4: update to 4.4.0.

Now uses meson as build system.

News in 4.4.0, 2019-09-09
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* Set NO_AT_BRIDGE=1 when running automated tests
* Speed up GtkSourceView rendering when space drawer is unused

News in 4.3.92, 2019-09-04
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* RC release for 4.4 scheduled for next week.
* New syntax highlighting definition file for: ASCII Doc, Dockerfile
* Improvements to the syntax highlighting of: CSS, Gradle, HTML, C, PHP,
  YAML, and Grovvy.
* Performance improvements in line number drawing.
* GtkSourceView now requires GTK 3.22 or newer.
* GtkSourceView no longer uses many deprecated APIs from GTK.
* GtkSourceView now uses fribidi directly to determine bidriectional
  direction for cursors.
* GtkSourceView now relies on GObject for correct marsharllers as well
  as va_marshallers or provides its own. This improves profiling with
  kernel stack unwinders such as Linux's perf.
* Visual column detection is improved to use the tab-width instead of
  the indent-width.
* Support for DnD from GIMPs color palette has been improved.
* A performance optimization has been added to avoid painting mark
  backgrounds if no GtkSourceMarks have been registered.
* Translation updates.

News in 4.3.1, 2019-04-23
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* Ported to meson build system, autotools will be phased out by next release.
* First release using `meson dist` instead of `make dist`. Distributions
  choosing to use autotools for this release will need to use autogen.sh.
* GtkSourceGutterRendererLines has gained an interger-to-string optimization
  to reduce the overhead of g_snprintf() in the vast majority of cases.
* Workaround a stack overflow in libpcre (via GRegex) in yaml.lang
* Improvements to the syntax highlighting of: fish, julia, and C++
* Translation updates.