ndk: <signal.h>: include <asm/sigcontext.h>

This patch modifies <signal.h>, starting from API level 8,
to include <asm/sigcontext.h>.

It is required to be able to use <signal.h> on a MIPS
platform. See https://android-review.googlesource.com/32281

Change-Id: I720259541fa7e2a4d6a428eae9fd4882c5355c31
1 file changed