Xyce requires names for .endl lines

# Issue
Xyce requires .endl statements to state the name of library that it is ending.

# Solution
Add corresponding library name to each .endl statement. 
To keep delta between ngspice and xyce models small  add them to ngspice model files too.

**example before**
```
lib tt
...
.endl
``` 

**example after**
```
lib tt
...
.endl tt
``` 