Unify NDK platform headers.

This commit removes duplication of system headers per platform, i.e. remove
copies of common headers like <stdlib.h> from arch-arm/usr/include and arch-x86/usr/include
and move them to a common include directory. More specifically:

- common headers:        android-N/arch-A/usr/include --> android-N/include
- arch-specific headers: android-N/arch-A/usr-include --> android-N/arch-A/include
- arch-specific libs:    android-N/arch-A/usr/lib     --> android-N/arch-A/lib

Change-Id: Ifdba5038d108901931f3e3a7c14ebe6270d2d276

NOTE: This also contains careful separation of API-level-specific headers.
      For example, platforms/android-5/include/pthread.h contains new function
      declarations that are not available when using platforms/android-3/include/pthread.h

NOTE: The NDK's build-platforms.sh script has been updated to understand the new
      layout. This change in develeopment/ndk does not change the layout of
      platform files under $NDK/platforms after build-platforms.sh is called.

ndk/platforms/android-3/arch-arm/include/asm/user.h

@@ -0,0 +1,61 @@
+/****************************************************************************
+ ****************************************************************************
+ ***
+ ***   This header was automatically generated from a Linux kernel header
+ ***   of the same name, to make information necessary for userspace to
+ ***   call into the kernel available to libc.  It contains only constants,
+ ***   structures, and macros generated from the original header, and thus,
+ ***   contains no copyrightable information.
+ ***
+ ****************************************************************************
+ ****************************************************************************/
+#ifndef _ARM_USER_H
+#define _ARM_USER_H
+
+#include <asm/page.h>
+#include <asm/ptrace.h>
+
+struct user_fp {
+ struct fp_reg {
+ unsigned int sign1:1;
+ unsigned int unused:15;
+ unsigned int sign2:1;
+ unsigned int exponent:14;
+ unsigned int j:1;
+ unsigned int mantissa1:31;
+ unsigned int mantissa0:32;
+ } fpregs[8];
+ unsigned int fpsr:32;
+ unsigned int fpcr:32;
+ unsigned char ftype[8];
+ unsigned int init_flag;
+};
+
+struct user{
+
+ struct pt_regs regs;
+
+ int u_fpvalid;
+
+ unsigned long int u_tsize;
+ unsigned long int u_dsize;
+ unsigned long int u_ssize;
+ unsigned long start_code;
+ unsigned long start_stack;
+ long int signal;
+ int reserved;
+ struct pt_regs * u_ar0;
+
+ unsigned long magic;
+ char u_comm[32];
+ int u_debugreg[8];
+ struct user_fp u_fp;
+ struct user_fp_struct * u_fp0;
+
+};
+#define NBPG PAGE_SIZE
+#define UPAGES 1
+#define HOST_TEXT_START_ADDR (u.start_code)
+#define HOST_STACK_END_ADDR (u.start_stack + u.u_ssize * NBPG)
+
+#endif