Missing MS CRT functionality in stddef.h

[JayFoxRox]

Here's a hack I've been using locally:

#FIXME: Need intptr_t in stddef.h
echo "#pragma once // Generated" > $NXDK_DIR/lib/xboxrt/libc_extensions/stddef_ext_.h
echo "#include <stdint.h>" >> $NXDK_DIR/lib/xboxrt/libc_extensions/stddef_ext_.h
echo "long long int _strtoi64(const char * nptr, char * * endptr, int base );" >> $NXDK_DIR/lib/xboxrt/libc_extensions/stddef_ext_.h
echo "unsigned long long int _strtoui64( const char * s, char ** endptr, int base );" >> $NXDK_DIR/lib/xboxrt/libc_extensions/stddef_ext_.h

There's more functionality in this, but this is enough for my current projects