Fix DrMemory warning in VS 2015 CRT

In VS 2015 builds every call to realloc triggers a warning like this:

Error #1: INVALID HEAP ARGUMENT: allocated with Windows API layer, queried with C library layer
  0 replace_malloc_usable_size
  1 _recalloc_base
  2 <lambda_4e60a939b0d047cfe11ddc22648dfba9>::operator()
  3 __crt_seh_guarded_call<>::operator()<>
  4 __acrt_lock_and_call<>
  5 _register_onexit_function
  6 _crt_atexit
  7 _onexit
  8 atexit
  9 testing::`dynamic initializer for 'FLAGS_gmock_verbose''

This mismatch is harmless (because the CRT always uses the Windows heap)
and out of our control. Therefore it should be suppressed.

With this suppression I now get a clean run on this previously failing
test:

tools\valgrind\chrome_tests.bat -t content_browsertests --tool \
    drmemory_light --build-dir=out\Release \
    --gtest_filter=ManifestBrowserTest.DummyManifest

BUG=440500,594808

Review URL: https://codereview.chromium.org/1813063002

Cr-Commit-Position: refs/heads/master@{#381840}

tools/valgrind/drmemory/suppressions.txt

@@ -74,6 +74,11 @@ name=https://github.com/DynamoRIO/drmemory/issues/68 (UNADDR 2)
 ...
 ntdll.dll!RtlValidateUnicodeString
 
+INVALID HEAP ARGUMENT
+name=realloc_size_HeapAlloc_mismatch
+drmemorylib.dll!replace_malloc_usable_size
+*!_recalloc_base
+
 ############################
 # TODO(timurrrr): investigate these
 UNADDRESSABLE ACCESS