Infer and trim padding at the end of TU sections

[ribbanya]

Given a TU with correctly assigned symbol sizes, dtk should be able to infer the unpadded endings of splits, like this:

 melee/ft/chara/ftPurin/ftPr_SpecialHi.c:
     .text       start:0x8013C9C8 end:0x8013CE8C
-     .sdata2     start:0x804D9C10 end:0x804D9C20
+     .sdata2     start:0x804D9C10 end:0x804D9C1C
 
 melee/ft/chara/ftPurin/ftPr_SpecialLw.c:
     .text       start:0x8013CE8C end:0x8013D234
     .sdata2     start:0x804D9C20 end:0x804D9C2C