Display correct line numbers for multiple .text sections (#63)

* Support multiple DWARF sequences

* Rework DWARF line info parsing

- Properly handles multiple sections
  in DWARF 1
- line_info moved into ObjSection
- DWARF 2 parser no longer errors with
  no .text section
- Both parsers properly skip empty
  sections

* Simplify line_info (no Option)

---------

Co-authored-by: Luke Street <luke.street@encounterpc.com>

objdiff-core/src/obj/mod.rs

@@ -39,6 +39,8 @@ pub struct ObjSection {
     pub symbols: Vec<ObjSymbol>,
     pub relocations: Vec<ObjReloc>,
     pub virtual_address: Option<u64>,
+    /// Line number info (.line or .debug_line section)
+    pub line_info: BTreeMap<u64, u64>,
 }
 
 #[derive(Debug, Clone, Eq, PartialEq)]
@@ -128,8 +130,6 @@ pub struct ObjInfo {
     pub sections: Vec<ObjSection>,
     /// Common BSS symbols
     pub common: Vec<ObjSymbol>,
-    /// Line number info (.line or .debug_line section)
-    pub line_info: Option<BTreeMap<u64, u64>>,
     /// Split object metadata (.note.split section)
     pub split_meta: Option<SplitMeta>,
 }