drcachesim's ifetch results are inflated from rep string expansion

Working on #1729 (closed) I saw that offline had fewer instruction fetches than online:

# bin64/drrun -t drcachesim -- suite/tests/bin/simple_app
---- <application exited with code 0> ----
Core #0 (1 thread(s))
  L1I stats:
    Hits:                          163,521
    Misses:                            793
    Miss rate:                        0.48%
  L1D stats:
    Hits:                           55,281
    Misses:                          2,098
    Miss rate:                        3.66%
Core #1 (0 thread(s))
Core #2 (0 thread(s))
Core #3 (0 thread(s))
LL stats:
    Hits:                              334
    Misses:                          2,557
    Local miss rate:                 88.45%
    Child hits:                    218,802
    Total miss rate:                  1.15%

# bin64/drrun -t drcachesim -offline -- suite/tests/bin/simple_app
# clients/bin64/drcachesim -indir drmemtrace.simple_app.32731.0000.dir/
Core #0 (1 thread(s))
  L1I stats:
    Hits:                          146,282
    Misses:                            793
    Miss rate:                        0.54%
  L1D stats:
    Hits:                           55,282
    Misses:                          2,095
    Miss rate:                        3.65%
Core #1 (0 thread(s))
Core #2 (0 thread(s))
Core #3 (0 thread(s))
LL stats:
    Hits:                              329
    Misses:                          2,559
    Local miss rate:                 88.61%
    Child hits:                    201,564
    Total miss rate:                  1.25%

That's a significant difference.

Online, disable bundles:
 L1I stats:
    Hits:                          160,887
    Misses:                            793

Tiny app is the same for both:

# bin64/drrun -t drcachesim -- /work/dr/test/allasm_x64
---- <application exited with code 0> ----
Core #0 (1 thread(s))
  L1I stats:
    Hits:                               39
    Misses:                              2
    Miss rate:                        4.88%
# bin64/drrun -t drcachesim -offline -- /work/dr/test/allasm_x64
# bin64/drrun -t drcachesim -indir drmemtrace.allasm_x64.10981.0000.dir/
Core #0 (1 thread(s))
  L1I stats:
    Hits:                               39
    Misses:                              2
    Miss rate:                        4.88%

Diffing simple_app, online has many more *4bb is the difference.

offline:
Instr 0x00007f82984464b0
Instr 0x00007f82984464b3
Instr 0x00007f82984464b7
Instr 0x00007f82984464ba
Instr 0x00007f82984464ba
Instr 0x00007f82984464ba

online:
Instr 0x00007fd6ea0fb4b0
Instr 0x00007fd6ea0fb4b3
Instr 0x00007fd6ea0fb4b7
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4ba
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4ba
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4bb
Instr 0x00007fd6ea0fb4ba

Online has 4 or 5 *4bb before every *4ba.

It's rep stos:

interp: start_pc = 0x00007fd6ea0fb4ba
  0x00007fd6ea0fb4ba  f3 aa                rep stos %al %rdi %rcx -> %es:(%rdi)[1byte] %rdi %rcx
  0x00007fd6ea0fb4bc  48 89 d0             mov    %rdx -> %rax

drutil uses 2 different translations: everything's xl8 is +1 except the stos or movs itself:

         *    rep movs
         * =>
         *    jecxz  zero
         *    jmp    iter
         *  zero:
         *    mov    $0x00000001 -> %ecx
         *    jmp    pre_loop
         *  iter:
         *    movs   %ds:(%esi) %esi %edi -> %es:(%edi) %esi %edi
         *  pre_loop:
         *    loop

Online is counting all those expanded instrs. I explicitly have code to not count them for offline. I'll address this by trying to do something similar for online.