kernel: improve uapi headers coexistence with musl

Make some network uapi headers detect if they are included after
not only glibc but also musl headers.

Signed-off-by: Jonas Gorski <jogo@openwrt.org>

SVN-Revision: 46161

target/linux/generic/patches-4.1/270-uapi-kernel.h-glibc-specific-inclusion-of-sysinfo.h.patch

@@ -0,0 +1,34 @@
+From 8b05e325824d3b38e52a7748b3b5dc34dc1c0f6d Mon Sep 17 00:00:00 2001
+From: David Heidelberger <david.heidelberger@ixit.cz>
+Date: Mon, 29 Jun 2015 14:37:54 +0200
+Subject: [PATCH 1/3] uapi/kernel.h: glibc specific inclusion of sysinfo.h
+
+including sysinfo.h from kernel.h makes no sense whatsoever,
+but removing it breaks glibc's userspace header,
+which includes kernel.h instead of sysinfo.h from their sys/sysinfo.h.
+this seems to be a historical mistake.
+on musl, including any header that uses kernel.h directly or indirectly
+plus sys/sysinfo.h will produce a compile error due to redefinition of
+struct sysinfo from sys/sysinfo.h.
+so for now, only include it on glibc or when including from kernel
+in order not to break their headers.
+
+Signed-off-by: John Spencer <maillist-linux@barfooze.de>
+Signed-off-by: David Heidelberger <david.heidelberger@ixit.cz>
+Signed-off-by: Jonas Gorski <jogo@openwrt.org>
+---
+ include/uapi/linux/kernel.h | 2 ++
+ 1 file changed, 2 insertions(+)
+
+--- a/include/uapi/linux/kernel.h
++++ b/include/uapi/linux/kernel.h
+@@ -1,7 +1,9 @@
+ #ifndef _UAPI_LINUX_KERNEL_H
+ #define _UAPI_LINUX_KERNEL_H
+ 
++#if defined(__KERNEL__) || defined( __GLIBC__)
+ #include <linux/sysinfo.h>
++#endif
+ 
+ /*
+  * 'kernel.h' contains some often-used function prototypes etc