Bug#1115169: vte2.91: stop using fmtlib embedded code copy

[Jeremy Bícha]

Source: vte2.91
Version: 0.82.0-1
Severity: important
Control: block -1 by 1114025

vte 0.82 is used a code copy of fmtlib because
- it was already included in the upstream tarball
- vte needs version >= 11 but that version is only in experimental

Once fmtlib >= 11 reaches unstable, vte should stop using the code copy.

Thank you,
Jeremy Bícha