[x265] rdcost: overflow check by integer

[Satoshi Nakagawa]

> Aside: Most systems I've seen seem to do this in via -D<...> or whatever.

It's simpler. Thanks.

# HG changeset patch
# User Satoshi Nakagawa <nakagawa424 at oki.com>
# Date 1400989083 -32400
#      Sun May 25 12:38:03 2014 +0900
# Node ID 54a0dc2278494f7ec3b74f3f06a8521c805af79a
# Parent  5e8cce428457f63fd9b8e18dafed2f8bed674d53
add -D__STDC_LIMIT_MACROS=1

diff -r 5e8cce428457 -r 54a0dc227849 source/CMakeLists.txt
--- a/source/CMakeLists.txt	Fri May 23 09:11:15 2014 -0500
+++ b/source/CMakeLists.txt	Sun May 25 12:38:03 2014 +0900
@@ -103,6 +103,8 @@
     endif()
 endif(MSVC)
 
+add_definitions(-D__STDC_LIMIT_MACROS=1)
+
 check_include_files(inttypes.h HAVE_INT_TYPES_H)
 if(HAVE_INT_TYPES_H)
     add_definitions(-DHAVE_INT_TYPES_H=1)