jvmfwk: pass along -Xss to JVM on AMD64 too

The PythonTest_dbacces_python in a clang ASAN build on F21 started to
fail with StackOverflowError in JNI_CreateJavaVM on the main thread,
and this fixes the problem.

Seen with java-1.8.0-openjdk-1.8.0.45-39.b14.fc21.x86_64

Change-Id: I87dfb4b62d547b334c19261aad88b4856489776f

jvmfwk/plugins/sunmajor/pluginlib/sunjavaplugin.cxx

@@ -67,7 +67,7 @@
 #endif
 #endif
 
-#if defined LINUX && defined X86
+#if defined LINUX && (defined X86 || defined X86_64)
 #include <sys/resource.h>
 #endif
 
@@ -755,7 +755,7 @@ javaPluginError jfw_plugin_startJavaVirtualMachine(
         options.push_back(Option("-Xint", nullptr));
     }
     if (!hasStackSize) {
-#if defined LINUX && defined X86
+#if defined LINUX && (defined X86 || defined X86_64)
         // At least OpenJDK 1.8.0's os::workaround_expand_exec_shield_cs_limit
         // (hotspot/src/os_cpu/linux_x86/vm/os_linux_x86.cpp) can mmap an rwx
         // page into the area that the main stack can grow down to according to