CLJS-3347: Create clojure.math namespace (#124)

* CLJS-3347: Create clojure.math namespace

This introduces the cljs.math namespace and clojure.core/abs for
parity with Clojure 1.11.0-alpha4.
Also introduces clojure.math-tests, which is an equivalent sets of
ClojureScript tests to the associated tests in Clojure.
Also include the Clojure test clojure.gen-math-test to compare
all reimplemented functions between the JVM versions and the
equivalent function calls executed on a ClojureScript prepl.

* Cleaned up references to Java Double in docs

Co-authored-by: Paula Gearon <gearon@gmail.com>

Author: swannodette

src/main/cljs/cljs/core.cljs

@@ -2712,6 +2712,11 @@ reduces them without incurring seq initialization"
   "Returns a number one less than num."
   [x] (- x 1))
 
+(defn ^number abs
+  {:doc "Returns the absolute value of a."
+   :added "1.11.10"}
+  [a] (Math/abs a))
+
 (defn ^number max
   "Returns the greatest of the nums."
   ([x] x)