Improve ARM function size inference

This allows 2-byte padding to be trimmed in ARM functions.

Resolves #253

objdiff-core/src/arch/mips.rs

@@ -355,6 +355,7 @@ impl Arch for ArchMips {
         while new_address >= symbol.address + 4
             && let Some(data) = section.data_range(new_address - 4, 4)
             && data == [0u8; 4]
+            && section.relocation_at(next_address - 4, 4).is_none()
         {
             new_address -= 4;
         }