Simplify package name
Import packaging fixes from libvmod-example
Fix wrong filename
Merge changes from libvmod-example
Check return type of variable and return error if it is wrong
Handle NULL in set_string

Varnish before 3.0.4 will pass NULL for a non-existent header.  People
should be running the latest version, but catch this anyway to avoid
segfaults.
Remove surplus vh_clear function and properly clear the memory area
during vh_init.
Line wrap
Harden variable vmod by using magic values, more asserts and treating
NULL string arguments as empty strings / no match consistently.
Fix missing locking in init function, causing race on the global id
array.