Stop Format/STEP.hpp Defining a Global fs Alias (#16102)

Every file that included STEP.hpp, directly or not, got namespace fs = boost::filesystem at global scope, and 29 sources and three headers relied on it without saying so. Headers now spell out boost::filesystem, and each source that uses fs declares the alias itself.

src/slic3r/GUI/DeviceManager.cpp

@@ -108,6 +108,8 @@
 
 #include "IPrinterAgent.hpp"
 
+namespace fs = boost::filesystem;
+
 #define CALI_DEBUG
 #define MINUTE_30 1800000    //ms
 #define TIME_OUT  5000       //ms