Improve Android support

This patch remove many Android-specific #ifdefs from the Breakpad
source code. This is achieved by providing "fixed-up" platform
headers (e.g. <signal.h> or <sys/user,h>), in the new directory
src/common/android/include/, which masks differences between
the NDK and GLibc headers.

The old "android_link.h" and "android_ucontext.h" are moved
and renamed.

This also requires putting this directory as the first
include path during Android-hosted builds, hence the
modification of Makefile.am and configure.ac
Review URL: https://breakpad.appspot.com/434002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1017 4c0a9323-5329-0410-9bdc-e9ce6186880e

src/client/linux/handler/exception_handler.h

@@ -37,10 +37,8 @@
 #include <signal.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <sys/ucontext.h>
 
-#if defined(__ANDROID__)
-#include "client/linux/android_ucontext.h"
-#endif
 #include "client/linux/crash_generation/crash_generation_client.h"
 #include "client/linux/handler/minidump_descriptor.h"
 #include "client/linux/minidump_writer/minidump_writer.h"