Add var-decl needles. Add short names to declarations in compiler plugin. Ref bug 1087465.
Add function-decl needles. Ref bug 1087465.
Add type-decl needles. Fix bug 1087465.

That's the last of the decl needles.
Remove the now-redundant test_c_vardecl.

Move its remaining useful "var:" test to test_vars. The "var-decl:" test was already covered by test_decl.