(_declare_item): accept pragmas
Assert pragmas (and other "executable" pragmas) are specifically allowed
in declare expressions, thanks to a recent AI22-0045. They are accepted
by the latest GNAT compilers.
Regenerate grammar using tree-sitter-linux-x64-0.20.7; add test.
Instead, package_declaration replaces it. This provides
better folding in nvim: otherwise, the final ';' was not
part of the tree node, and thus the last line "end P;" was
not folded.
