Refresh prebuilts/ndk/android-ndk-r8 with content of r8c

Mostly notable change is the removal of arch-x86 and arch-mips headers
from platforms/android-{3,4,5,8}. Those headers are imcomplete to begin
with, since both X86 and MIPS ABIs are only supported at API > 8

Other fixes (excerpts from docs/CHANGES.html)

1. Fixed arch-mips/include/asm/* previously incorrectly cleaned from original kernel
   See https://android-review.googlesource.com/#/c/43335
2. Replace struct member data "__unused" with "__linux_unused" in linux/sysctl.h
   and linux/icmp.h to avoid conflict with "#define __unused" in sys/cdefs.h
3. Fixed fenv.h to enclosed C functions with __BEGIN_DECLS/__END_DECLS
4. Removed unimplemented functions in malloc.h
5. Fixed stdint.h.  See http://code.google.com/p/android/issues/detail?id=1952
6. Fixed preprocessor macros in <arch>/include/machine/*
7. Replaced link.h for mips with new version for all platforms
8. Remove linux-unistd.h

Change-Id: Idec3b7cf3402ae614e7a92d14d44d734dea7259d
5314 files changed