Setup PcFileCache stubs and ctor tests
Add a test for PcFileCache.GetPackages()
Remove redundant pc info store.

* PcFileCache.filesByFolders held copies of the package infos in
  PcFileCache.infos grouped by the resp. pkg config directories the pc files
  resided in.

* Rewrite GetPackages:
    - Returns a snapshot-in-time IEnumerable<PackageInfo> ordered by pkg config
      folder.
    - Noramilzes paths of pkgConfigDirs parameter

* Remove now superfluous method PcFileCache.Add(,,)
Remove obsolete pc infos from pc cache on Update()

The pc info file cache (~/.config/xbuild/pkgconfig-cache-2.xml) stored data
for files which don't exist anymore on the system which causes
https://bugzilla.xamarin.com/show_bug.cgi?id=11133.

This patch removes obsolete entries from the cache when
PcFileCache.Update() is called.
Avoid adjusting selection twice in TextControl.

This commit licensed as MIT/X11.
Implementation of System.Reflection.ParameterInfo.HasDefaultValue
Merge pull request #838 from desdesdes/master

Implementation of System.Reflection.ParameterInfo.HasDefaultValue
Merge pull request #849 from antoniusriha/pcCacheBug

Fix for PkgConfig cache orphaned entries bug (xam bug #11133)
Merge pull request #822 from carlosmn/asp-pc

Use full path for aspnetwebstack pkg-config file
[aot] Sanitize utf8 characters in symbol names. Fixes #16851.
Remove usage of mini_replace_type () from mono_jit_runtime_invoke (), runtime invokes care about the precise types of parameters. Fixes #16830.
Change System.Windows.Forms.DataVisualization PKT to match Windows.

This commit licensed as MIT/X11.
Avoid infinite loop in property getter.

This commit licensed as MIT/X11.
Implement GroupDescription based on moonlight implementation
[sdb] The sdb library depends on Process.Start returning a Process object, so force UseShellExecute to false.

This fixes a massive breakage on wrench.
[jit] Avoid nullifying class init trampolines for recursive calls to class initializers. Fixes #16489
Merge pull request #859 from antoniusriha/groupDescription

Implement GroupDescription based on moonlight implementation
Merge pull request #858 from madewokherd/datavis

System.Windows.Forms.DataVisualization fixes
[gsharedvt] Avoid using the variable size code paths for non-variable size types with some array opcodes. Fixes #17023.
[mcs] Await flow analysis uses resolved expression. Fixes #16840