test(spec): macros, reader, host-interop, namespaces — fix def-doc, resolve, %&

Final spec areas. Bugs caught and fixed:
- (def name docstring value) used the docstring as the value; now the 3-arg
  docstring form binds the value and records :doc meta
- resolve was a nil stub; now a special form resolving a symbol to its var
  (nil if unresolved). Added find-ns (non-creating lookup) and ns-name.
- in-ns didn't evaluate its arg, so (in-ns 'foo) failed; now evaluates it per
  Clojure (the integration test's unquoted form updated to the quoted idiom)
- #(... %& ...) built %& as a positional param instead of a & rest param;
  now emits (fn* [... & gen] ...) so %& captures the rest

Full public-API spec layer now in place. conformance 218/218, jpm test green.

test/spec/reader-syntax-spec.janet

@@ -0,0 +1,38 @@
+# Specification: reader syntax & literals.
+(use ../support/harness)
+
+(defspec "reader / scalar literals"
+  ["integer"            "42"        "42"]
+  ["negative"           "-7"        "-7"]
+  ["float"              "1.5"       "1.5"]
+  ["string"             "\"hi\""    "\"hi\""]
+  ["boolean true"       "true"      "true"]
+  ["nil"                "nil"       "nil"]
+  ["keyword"            ":a"        ":a"]
+  ["namespaced keyword" "true"      "(= :a/b :a/b)"]
+  ["char"               "\\a"       "\\a"]
+  ["char newline"       "true"      "(= \\newline (first \"\\n\"))"]
+  ["ratio not supported but reads ints" "3" "3"]
+  ["hex literal"        "255"       "0xff"]
+  ["symbol via quote"   "'foo"       "'foo"])
+
+(defspec "reader / collection literals"
+  ["vector"             "[1 2 3]"   "[1 2 3]"]
+  ["list quoted"        "[1 2 3]"   "'(1 2 3)"]
+  ["map"                "{:a 1}"    "{:a 1}"]
+  ["set"                "#{1 2 3}"  "#{1 2 3}"]
+  ["nested"             "{:a [1 {:b 2}]}" "{:a [1 {:b 2}]}"]
+  ["empty vector"       "[]"        "[]"]
+  ["empty map"          "{}"        "{}"]
+  ["empty set"          "#{}"       "#{}"])
+
+(defspec "reader / dispatch & sugar"
+  ["anon fn #()"        "3"         "(#(+ %1 %2) 1 2)"]
+  ["anon fn single %"   "2"        "(#(inc %) 1)"]
+  ["anon fn %&"         "[2 3]"     "(#(vec %&) 2 3)"]
+  ["discard #_"         "[1 3]"     "[1 #_2 3]"]
+  ["regex literal"      "true"      "(= \"abc\" (re-find #\"abc\" \"xabcx\"))"]
+  ["reader conditional" "1"         "#?(:clj 1 :cljs 2 :default 3)"]
+  ["tagged literal var" "true"      "(var? #'+)"]
+  ["deref sugar"        "5"         "(let [a (atom 5)] @a)"]
+  ["meta sugar"         "{:t 1}"    "(meta ^{:t 1} [])"])