make with-android-headers optional

If --with-android-headers is not specified, try to use pkg-config.

Also, extract Android versions from android-version.h using
ANDROID_HEADERS_CFLAGS and the preprocessor.

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
Don't use the android/ prefix in #includes
Ensure all Makefile.am have ANDROID_HEADERS_CFLAGS to avoid the android/ prefix in #include

[adrian] use ANDROID_HEADERS_CFLAGS instead of '-Itop_srcdir/include/android -Itop_srcdir/include/android/libnfc-nxp'

Signed-off-by: David Greaves <david@dgreaves.com>
Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
remove unused gralloc param

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
remove un-defined egl_create_image_wl

Signed-off-by: Adrian Negreanu <adrian.m.negreanu@intel.com>
extract bionic kernel headers

This patch correctly extracts bionic kernel headers instead
of those under external/kernel-headers/original/.

From external/kernel-headers/original/README.txt:
  This directory contains the original kernel headers that are used to generate Bionic's "cleaned-up" user-land headers.
  They are mostly covered by the GPLv2 + exception, and thus cannot be distributed as part of the platform itself.
  (NOTE: The cleaned up headers do not contain copyrightable information and are distributed with Bionic)
Merge pull request #195 from groleo/cleanups

Cleanups
Merge pull request #197 from groleo/alterego-use-kernel-headers-from-bionic

extract bionic kernel headers