sim/erc32: Switched emulated memory to host endian order.

Change data ordering in emulated memory from target order (big endian)
to host order. Improves performance and simplifies most memory
operations. Requires some byte twisting during stores on little
endian hosts (intel). Also removed support for little-endian binaries.

sim/erc32/sis.c

@@ -223,7 +223,11 @@ main(argc, argv)
     sregs.freq = freq;
 
     INIT_DISASSEMBLE_INFO(dinfo, stdout, (fprintf_ftype) fprintf);
+#ifdef HOST_LITTLE_ENDIAN
+    dinfo.endian = BFD_ENDIAN_LITTLE;
+#else
     dinfo.endian = BFD_ENDIAN_BIG;
+#endif
 
     termsave = fcntl(0, F_GETFL, 0);
     using_history();