Add sk_calloc.  Remove SkMemory_stdlib, which seems unused.

I'm seeing basically no difference between malloc + bzero and calloc on my desktop, but on a Galaxy Nexus calloc is never slower, and significantly faster once the allocation size becomes large, both for allocation and for _reading_.

BUG=skia:1662
R=reed@google.com

Review URL: https://codereview.chromium.org/24251008

git-svn-id: http://skia.googlecode.com/svn/trunk/gyp@11414 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests.gyp b/tests.gyp
index 43acd94..c67e578 100644
--- a/tests.gyp
+++ b/tests.gyp
@@ -81,6 +81,7 @@
         '../tests/MathTest.cpp',
         '../tests/MatrixTest.cpp',
         '../tests/Matrix44Test.cpp',
+        '../tests/MemoryTest.cpp',
         '../tests/MemsetTest.cpp',
         '../tests/MetaDataTest.cpp',
         '../tests/MipMapTest.cpp',