Add propagate function and opcode

This allows better stacktraces when manually intercepting
signals to clean up resources. Also allows functionality
from Common Lisp's unwind-protect, such as calling cleanup code
while unwindinding the stack, restarting on certain signals, and
just in general having more control over signal and signal propagation.

Also fix a bug encountered while implementing with-resource in the
compiler. Desturcturing arguments that were not the last argument
would often result in bad code generation, as slots used to destructure
the earlier arguments would invalidate the later parameters. This is
fixed by allocating all named parameters before doing any destructuring.

test/suite7.janet

@@ -88,4 +88,21 @@
 (assert (peg/match p "abc") "complex peg grammar 1")
 (assert (peg/match p "[1 2 3 4]") "complex peg grammar 2")
 
+#
+# fn compilation special
+#
+(defn myfn1 [[x y z] & more]
+  more)
+(defn myfn2 [head & more]
+  more)
+(assert (= (myfn1 [1 2 3] 4 5 6) (myfn2 [:a :b :c] 4 5 6)) "destructuring and varargs")
+
+#
+# Test propagation of signals via fibers
+#
+
+(def f (fiber/new (fn [] (error :abc) 1) :ei))
+(def res (resume f))
+(assert-error :abc (propagate res f) "propagate 1")
+
 (end-suite)