* include/libabigail: New directory.
* include/Makefile.am: New file.
* include/libabigail/Makefile.am: New file.
* src/abg-*.h: Move these in include/libabigail/*.h
* src/Makefile.am: Set -I option to look for headers in include/libabigail
* doc/api/libabigail.doxy: Look for headers in include/libabigail
* tests/Makefile.am: Set -I option to look for headers in include/libabigail
* abigail.m4: Set includedir to $prefix/include/libabigail for
library used as a dep, or to srcdir/libabigail/include/libabigail
in GCC source tree.
* configure.ac: Add Makefile.am in include and include/libabigail
* abigail.m4: Look for headers in include/libabigail when the
libabigail is in in the source tree and in $incdir/libabigail when
it is installed as a dependency.