[#1] Updated the library to compile for Rust 2021.

This was mostly just a change to the cargo edition target.

I also went and removed the weave requirement. It was just a function
wrapper around the ? operator that was new at that time. As this has
become very common place I just swapped the code over to it.

src/c_flags.rs

@@ -186,7 +186,7 @@ macro_rules! c_flags
             let mut first: bool;
 
             // Push the left bracket onto the string.
-            weave::attempt!(write!(f, "{}", '{'));
+            write!(f, "{}", '{')?;
 
             // Handle checking each flag to see if it
             // is part of this flag.
@@ -198,11 +198,11 @@ macro_rules! c_flags
                   // then add an OR symbol.
                   if first == false
                   {
-                     weave::attempt!(write!(f, " | "));
+                     write!(f, " | ")?;
                   }
 
                   // Push the flags name onto the string.
-                  weave::attempt!(write!(f, "{}", stringify!($flag)));
+                  write!(f, "{}", stringify!($flag))?;
                   first = false;
                }
             )+
@@ -211,7 +211,7 @@ macro_rules! c_flags
             if first == true
             {
                // Put a space in the string.
-               weave::attempt!(write!(f, " "));
+               write!(f, " ")?;
             }
 
             // Push the right bracket onto the string