Fix copying of prebuilt SDL library

The test on $(SDL_CONFIG) needs to come after "include Makefile.android",
because that variable is set in Makefile.common, which is included from
Makefile.android.
Detect a PPC host also when the kernel is 64-bit

On a 64-bit kernel "uname -m" will return "ppc64", not "powerpc", so
handle that...
Add missing target disassembler for x86
Only enable KVM support for x86 target if host is also x86
Set the correct GLES libname also on powerpc
libjpeg: Only enable SSE2 on x86 hosts
goldfish_fb: Fix typo in endian conversion code
Fix endianness bug in skin_image_load

The file android/skin/image.c includes SDL_config.h, but not
config-host.h.  Therefore using HOST_WORDS_BIGENDIAN will not
work, but using SDL_BYTEORDER will.