Refactor macro handling: add pascal_to_snake utility, rewrite Target handling, and update descriptor structure for bits-based targets.

crates/pmp-core/src/functions.rs

@@ -24,3 +24,26 @@ pub fn snake_to_title(s: &str) -> String
         .collect::<Vec<_>>()
         .join(" ")
 }
+
+pub fn pascal_to_snake(s: &str) -> String
+{
+    let mut out = String::with_capacity(s.len());
+    let mut prev_lower = false;
+
+    for c in s.chars()
+    {
+        if c.is_uppercase()
+        {
+            if prev_lower              { out.push('_'); }
+            for lc in c.to_lowercase() { out.push(lc); }
+            prev_lower = false;
+        }
+        else
+        {
+            prev_lower = true;
+            out.push(c);
+        }
+    }
+
+    out
+}