Environment: Refactoring and cleanup
Fixed #4876 (Checking for sizeof(void))
Revert "GUI: Added --std setting for GTK"

This reverts commit 5f5fdab650321f0a9845cc0af5ecd860fcb76afe.

The --std setting for GTK has been removed
Fixed #4893 (FP Uninitialized variable on sizeof of itself)