Speed up saving PNGs by skipping a null transform

Closes #90

See merge request !14

Calling png_set_shift to set the number of significant bits of input
triggers a transform operation inside libpng which shifts bits around,
even if it's a null operation of 8 bits to 8 bits.

I measured this slowdown as about 30% of total saving runtime on a
large 7680x2160 screenshot.

In addition, only 8 bits per channel are supported in gdk-pixbuf so
this is never actually needed in practice...

Skipping the png_set_shift call altogether doesn't change output and
speeds it up nicely.

Fixes #90

Ensure that building loaders.cache depends on modules

Closes #88

See merge request !13

We're passing the full path to the shared modules, which confuses Meson.

Closes #88

A copy and paste thinko on the GDK_PIXBUF_UNAVAILABLE_IN_* macros after
2.22 generated the exact same warning for all releases after that.

This commit introduces no functional change, only an updated compiler
warning with the correct version numbers.

Group the sections that are deprecated or that defer to another library,
to ensure that readers are aware of their status at a glance.

We did not introduce any new symbol, but it's good project hygiene to
always have per-release version macros as part of the release process.

We need to use the ulink element, not the link one, for URLs.

We regenerate the types file every time we build the documentation, to
avoid missing types.

A couple clarifications of the wording in the build instruction.

Make the README a bit more helpful.

The read_pixels() method is missing a `Returns` stanza.

The read_pixels_bytes() method is missing a description.

Both functions do the same thing, so they should be documented
similarly.

Drop the conditional support on get_supported_link_arguments(), as there
have been multiple stable releases of Meson with that method.

Clarify pixels vs. bytes

See merge request !6

One needs to pass in -Dx11=false as well, for all Visual Studio builds.

This tells people that building on Visual Studio is now done using Meson
and outlines the steps that are required for the build.

It already takes about 20 seconds on my Core i7, and it can get worse
when running multiple tests in parallel, so it's a prime candidate for
timeouts on our CI infrastructure.

Bastien Nocera authored Dec 13, 2016 and Emmanuele Bassi committed Jun 29, 2018

https://bugzilla.gnome.org/show_bug.cgi?id=775229

We don't need them any more.

tiff: fix include of windows.h on case-sensitive filesystems

See merge request !10

On case-sensitive filesystems, such as when cross-compiling from Linux,
including Windows.h will result in an error.

We generate a random builddir, so we need to modify the `paths` key for
the artifacts we store on CI failure.

We're not using Bugzilla any more.

Few fixes for Visual Studio builds

See merge request !8

Visual Studio builds do not assume the presence of a shell script
interpreter but would normally use cmd.exe, which would make the post
install shell script useless in such situations.

Fix this by adding a Windows .bat port of the post install script, to be
used on Visual Studio builds, which may be usable on MinGW builds if
MinGW builds can be done directly in cmd.exe.

Fix the checks as set10() will still set the macros to 0, which will
break the build when we compile conditionally using #if[n]def.