make spacing in x86_64 alltypes.h.sh more uniform with other archs

patch by Luka Perkov, who noted that all other archs have a newline.

arch/x86_64/bits/alltypes.h.sh

@@ -19,6 +19,7 @@ union \1 \2;\
 TYPEDEF unsigned long size_t;
 TYPEDEF long ssize_t;
 TYPEDEF long ptrdiff_t;
+
 TYPEDEF __builtin_va_list va_list;
 TYPEDEF __builtin_va_list __isoc_va_list;