serf: Fix building with unified headers

[termux-packages] / ndk_patches_unified / syscall.h.patch

--- /home/fornwall/lib/android-ndk/platforms/android-21/arch-arm/usr/include/syscall.h	2016-12-03 21:40:40.033159200 +0530
+++ ./usr/include/syscall.h	2016-12-03 19:52:16.226951188 +0530
@@ -0,0 +1 @@
+#include <sys/syscall.h>