For regular modules, adding files to BLOBS is sufficient to create the
corresponding headers.
Application modules are different, as they use a minimal makefile
(makefiles.application.inc.mk) to build, thus application level
variables are not available.
This commit makes Makefile.include pass BLOBS to the application
Makefile as APPLICATION_BLOBS, and application.inc.mk use that variable
as value for BLOBS.
The indirection is necessary so submakefiles (e.g., those visited by
DIRS) do not hard override BLOBS.
Set the application module name with APPLICATION_MODULE.
The default module name is "application_$(APPLICATION)".
This should fix name conflicts where an application/test has the same name as
an existing module and so both write to the same archive.
