Comprehensive documentation covering implementation phases, testing procedures,
and usage guides for the DWARF v4 debugging support.

This commit fixes two critical bugs preventing DWARF sections from
appearing in compiled binaries:

1. Fixed output channel bug in arm64/emit.mlp:
   - Changed emit_dwarf from writing to stdout to using !Emitaux.output_channel
   - Added create_asm_file check to match amd64 implementation
   - This ensures DWARF sections are written to the .s file, not discarded

2. Fixed symbol naming in emitaux.ml for DWARF relocations:
   - Implemented format_symbol_for_dwarf function matching emit_symbol logic
   - Adds _ prefix on macOS for Mach-O compatibility
   - Properly escapes special characters (@, ^^, etc.) using $$XX hex encoding
   - Uses Compilenv.symbol_separator and escape_prefix for consistency

Result:
- Object files now contain all DWARF sections (__debug_info, __debug_abbrev,
  __debug_str, __debug_line)
- dsymutil successfully extracts complete debugging information
- Verified with dwarfdump showing function names, types, and compilation units

Updated documentation to reflect that the DWARF implementation bugs have
been fixed and all tests are passing:

1. TOOLCHAIN_INTEGRATION_SOLUTION.md:
   - Changed status from "macOS Limitation" to "RESOLVED ✅"
   - Documented the two actual bugs that were fixed:
     * Bug #1: DWARF sections written to stdout instead of assembly file
     * Bug ocaml#2: Symbol names not properly escaped for assembler
   - Removed incorrect conclusion about macOS toolchain limitations
   - Added verification steps showing all DWARF sections present

2. DWARF_TEST_RESULTS.md:
   - Updated status to "ALL TESTS PASSING"
   - Added verification report showing 4/4 DWARF sections in all tests
   - Documented test coverage: test_simple, test_basic, test_debug, test_types
   - Confirmed debugger compatibility (dwarfdump, dsymutil, lldb, gdb)
   - Listed all 8 working features (line tables, functions, types, etc.)

3. verify_dwarf.sh:
   - Added automated verification script
   - Checks all test programs for DWARF sections
   - Verifies function count and dSYM extraction

All tests verified:
- test_simple: 2 functions, 4 DWARF sections ✓
- test_basic: 7 functions, 4 DWARF sections ✓
- test_debug: 5 functions, 4 DWARF sections ✓
- test_types: 13 functions, 4 DWARF sections ✓

Add comprehensive type support for OCaml primitive types in DWARF debugging
information. This completes Milestone 1 of the Phase 5-6 roadmap.

Changes:
- Extended type_offsets to include 7 primitive types (was 2, now 7)
- Added type DIEs for: float, char, bool, string, unit
- Calculated proper DWARF offsets for each type (0x19-0x43 range)
- Used appropriate DW_ATE_* encodings for each type:
  * float: DW_ATE_float (IEEE 754 double)
  * char: DW_ATE_unsigned_char (8-bit)
  * bool: DW_ATE_boolean
  * string: DW_ATE_address (pointer to string block)
  * unit: DW_ATE_address (constant value)

Technical details:
- Each type DIE is ~7 bytes in .debug_info section
- Offsets calculated based on CU DIE structure
- Maintains backward compatibility with existing int and value types
- All types initialized automatically in dwarf.ml

Impact:
- GDB/LLDB can now distinguish all OCaml primitive types
- 'info types' shows complete type information
- Foundation for future complex type implementations
- ~14% progress toward completing Phases 5-6 (1 of 7 milestones)

Testing:
- Added test_enhanced_types.ml exercising all primitive types
- Full rebuild required to test (stdlib must be recompiled)

Documentation:
- Added PHASE5_6_IMPLEMENTATION.md with complete technical details
- Documented type representations, offset calculations, and next steps