LibDebug: Support addrx*, strx* and rnglistx forms

These forms were introduced in DWARF5, and have a fair deal of
advantages over the more traditional encodings: they reduce the size of
the binary and the number of relocations.

GCC does not emit these with `-g1` by default, but Clang does at all
debug levels.

Userland/Libraries/LibDebug/CMakeLists.txt

@@ -3,6 +3,7 @@ set(SOURCES
     DebugSession.cpp
     Dwarf/AbbreviationsMap.cpp
     Dwarf/AddressRanges.cpp
+    Dwarf/AttributeValue.cpp
     Dwarf/CompilationUnit.cpp
     Dwarf/DIE.cpp
     Dwarf/DwarfInfo.cpp