cmd/5l: move offset2 into Adr.u0 union to save 4/8 bytes for Adr/Prog resp. sizeof(Adr) from 24 bytes down to 20 bytes. sizeof(Prog) from 84 bytes down to 76 bytes.
cmd/5l: move offset2 into Adr.u0 union to save 4/8 bytes for Adr/Prog resp.
sizeof(Adr) from 24 bytes down to 20 bytes.
sizeof(Prog) from 84 bytes down to 76 bytes.

5l linking cmd/godoc statistics:
Before:
Maximum resident set size (kbytes): 106668
After:
Maximum resident set size (kbytes):  99412

R=golang-dev, dave
CC=golang-dev
https://codereview.appspot.com/7100059

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