Fix a problem which occurred when a function type was forward-referenced by parameter types. This was intended to fix the following test case: {{{ void delegate(Hit) dg; struct Hit { void delegate(Hit) a; } }}} which ChristianK reduced from a problem downs had on IRC. It also seems to fix mini/compile_delegate.d (which turns out to be quite similar, but produced a different error message).

[Environment]
DFLAGS=-I@RUNTIME_DIR@/import -L-L%@P%/../lib -defaultlib=@RUNTIME_AIO@ -debuglib=@RUNTIME_AIO@