Cross-platform packaging manifests

I have had several bugs recently that required changes to the packaging 
manifests in xpinstall/packager and embedding/config.  Most of these 
changes were exactly the same on each platform, and involved lots of 
grunt work and potential for error.

In addition, many of the embedding and GRE manifests in embedding/config 
duplicate the manifests in xpinstall/packager.

I have been thinking of a way of combining these manifests in a tiered, 
cross-platform manner.

GOALS:

1) to reduce the number of files that must be touched when a patch 
alters packaging
2) to increase the clarity of which manifests package which products

PROPOSAL:

I think that we can "tier" packaging files like so:
minimo.manifest
embedding.manifest
GRE.manifest
XRE.manifest (if/when this ever happens)

Then, each application (seamonkey/*Bird) would have an 
application-specific packaging script (in the case of seamonkey, 
multiple scripts, one for each XPI (browser/mail/etc).

The format of each packaging script would be unified so that we could 
use the same format for all platforms, without worrying about 
differences (lib*.so/*.dll/.shlb). Also, each file could have optional 
platform-specific sections. Something like this:

ALL
	components/intl.xpt
	res/charsetalias.properties
	res/charsetData.properties
	res/langGroups.properties
	res/language.properties

ALL-NONSTATIC
	components/{lib}i18n.{so}

UNIX
	res/unixcharset.properties

WIN32
	res/wincharset.properties

MAC
	res/maccharset.properties