Log Message:
libsass/sassc: updated to 3.4.7

3.4.7:
Features
* Implement exponents for numbers
* Implement long file path support for Windows

Fixes
* Error on quoted string in simple selector parsing
* Do not compress colors in selectors
* Fix issue when passing restargs to call
* Fix issue with attribute selector unification
* Improve wrapped pseudo selector handling
* Improve extend of wrapped pseudo selectors
* Fix propagation of named rest arguments
* Do not output invisible support blocks
* Various build makefile and CI related fixes