Add sk_calloc. Remove SkMemory_stdlib, which seems unused.

tests/MemoryTest.cpp

Index: tests/MemoryTest.cpp
diff --git a/tests/MemoryTest.cpp b/tests/MemoryTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..4c3216b83b9af1f803ac96827c097c1c9ef0bba1
--- /dev/null
+++ b/tests/MemoryTest.cpp
@@ -0,0 +1,12 @@
+#include "Test.h"
+#include "TestClassDef.h"
+
+DEF_TEST(memory_calloc, reporter) {
+    const size_t kNum = 200;
+    char* zeros = (char*)sk_calloc_throw(kNum*sizeof(char));
+
+    for (size_t i = 0; i < kNum; i++) {
+        REPORTER_ASSERT(reporter, 0 == zeros[i]);
+    }
+    sk_free(zeros);
+}