Validate splits don't overlap symbols (or each other)

Use DoubleEndedIterator::next_back instead of Iterator::last to avoid unnecessary iteration.

src/analysis/slices.rs

@@ -80,7 +80,7 @@ impl FunctionSlices {
 
     pub fn add_block_start(&mut self, addr: u32) -> bool {
         // Slice previous block.
-        if let Some((_, end)) = self.blocks.range_mut(..addr).last() {
+        if let Some((_, end)) = self.blocks.range_mut(..addr).next_back() {
             let last_end = *end;
             if last_end > addr {
                 *end = addr;

src/analysis/tracker.rs

@@ -376,7 +376,7 @@ impl Tracker {
         if self.ignore_addresses.contains(&addr) {
             return false;
         }
-        if let Some((&start, &end)) = obj.blocked_ranges.range(..=from).last() {
+        if let Some((&start, &end)) = obj.blocked_ranges.range(..=from).next_back() {
             if from >= start && from < end {
                 return false;
             }