std.conv: Fix ambiguity when target has ctor and source has opCast
std.array: Allow joining constant arrays
Fix issue 10958 - Variant fails to compile for types with sizeof == 0.
Add assignment to EmptyArray.init to prevent use before set error.
Fixed unittests to include original, proper, test case.
Fix Issue 12046 - Disallow Rebindable!(T[N])

https://d.puremagic.com/issues/show_bug.cgi?id=12046
Merge pull request #1943 from Poita/bug12046

Fix Issue 12046 - Disallow Rebindable!(T[N])
Merge pull request #1936 from Kapps/fix10958

Fix issue 10958 - Variant fails to compile for types with sizeof == 0.
Merge pull request #1865 from CyberShadow/std-array-join-const

std.array: Allow joining constant arrays
Merge pull request #1864 from CyberShadow/std-conv-opcall-and-ctor

std.conv: Fix ambiguity when target has ctor and source has opCast