Merge: text: escape_to_mk should not escape =

Remove the escaping to ASCII hex value for the `=` char in `escape_to_mk`. It doesn't appear to be necessary, it was not documented and it breaks `nitls` support for `nitpm` packages.

Here's the error raised by `make` when it can't parse an escaped `=`.
~~~
make: *** No rule to make target '/home/xymus/.local/lib/nit/gamnit?3ddepth-vbos/lib/gamnit/bmfont.nit'
~~~

Pull-Request: #2713