Makefile: Whitespace cleanup

Indent our Makefiles using only tabs with width 8.
Also keep all escaped new-lines aligned on column 72. 72 might seem
like a high number but it ensures that the \'s will keep being aligned
without adding realignment noise to patches in the future.

https://bugzilla.gnome.org/show_bug.cgi?id=722338
Rename data resource file

Add ".data" to the data resource file. This is in preparation for a
coming patch where I will add a ".js" resource file and I want
consistent naming.

https://bugzilla.gnome.org/show_bug.cgi?id=722338
Make gnome-maps a binary

Make gnome-maps a small C program that loads JS from an included
GResource.

https://bugzilla.gnome.org/show_bug.cgi?id=722338
Gitignore: ignore C-stuff

Turning gnome-maps into a C binary produces more intermediate files.
Let's ignore those.

https://bugzilla.gnome.org/show_bug.cgi?id=722338