Merge pull request #186 from lbt/master

Introduce android-config.h to ensure build-time defines can be set
Fix stupid error in comment

Signed-off-by: David Greaves <david@dgreaves.com>
Don't use the android/ prefix in #includes
Ensure all Makefile.am have -I$(top_srcdir)/include/android to avoid android/ prefix in #includes

Signed-off-by: David Greaves <david@dgreaves.com>
Modify extract headers.sh to take optional args for pkgconfig and version:
 extract-headers.sh ANDROID_ROOT HEADERPATH [--version MAJOR.MINOR.PATCH.[PATCH2].[PATCH3]] [--pkgconfigpath <installed header path>]
--version and --pkgconfigpath can be shortened to -v and -p
A pkgconfig android-headers.pc file is now dropped in the HEADERPATH for relocation by packagers. This .pc works with the removal of android/ prefix from headers

Signed-off-by: David Greaves <david@dgreaves.com>