Allow for overrididing INSTALL_HEADER_FILES

Change-Id: If6aa9be1742521d58ef825d2356bace3a0694a2c
Reviewed-on: http://review.couchbase.org/32675
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>
Use CMake as the toplevel makefile

Change-Id: I139aa0f9ed0687a494b97d28026f3fbe56ffb2e8
Testing wiht a modified layout

Change-Id: Ifdb422172781644abfb3be61888f7702980989d1