fix Issue 12531 - forward reference with nested struct
Merge pull request #3899 from 9rnsr/fix12531

Issue 12531 - forward reference with nested struct
[Refactoring] fix indent in IsExp::semantic()
fix Issue 13350 - is(typeof(fun)) causes link error when template fun calls undefined reference

Evaluate the type in InExp, then unspeculative declared symbols.
+1
+1a
+bugfix
-clean
-clean2
fix link846.d
+2
-reduce indent
+2a
+2b
fix runnable/A16.d
+clean & a little fix in unSpeculative
+clean2
+clean3 Rename instMod -> tinstModule -> minst
Remove unused function TemplateDeclaration::getInstantiating
+test