-Waggressive-loop-optimizations warnings

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audio/mpeglayer3.cpp: In function 'void layer3reorder_1(int, int, REAL (*)[18], REAL (*)[18])':
audio/mpeglayer3.cpp:1287:33: warning: iteration 9 invokes undefined behavior [-Waggressive-loop-optimizations]
 1287 |  (sfb_lines=sfBandIndex->s[sfb+1]-sfb_start))
      |             ~~~~~~~~~~~~~~~~~~~~^
audio/mpeglayer3.cpp:1285:10: note: within this loop
 1285 |       sfb<13;
      |       ~~~^~~
audio/mpeglayer3.cpp: In function 'void layer3reorder_2(int, int, REAL (*)[18], REAL (*)[18])':
audio/mpeglayer3.cpp:1312:33: warning: iteration 12 invokes undefined behavior [-Waggressive-loop-optimizations]
 1312 |  (sfb_lines=sfBandIndex->s[sfb+1]-sfb_start))
      |             ~~~~~~~~~~~~~~~~~~~~^
audio/mpeglayer3.cpp:1310:10: note: within this loop
 1310 |       sfb<13;
      |       ~~~^~~

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Related: gcc-4.4 and gcc-4.5 emit the following warnings:

audio/mpeglayer3.cpp: In member function ‘void MPEGaudio::layer3dequantizesample(int, int, int (*)[18], REAL (*)[18])’:
audio/mpeglayer3.cpp:957: warning: array subscript is above array bounds
audio/mpeglayer3.cpp:957: warning: array subscript is above array bounds
audio/mpeglayer3.cpp: In member function ‘void MPEGaudio::layer3fixtostereo(int, REAL (*)[32][18])’:
audio/mpeglayer3.cpp:1067: warning: array subscript is above array bounds
audio/mpeglayer3.cpp:1167: warning: array subscript is above array bounds
audio/mpeglayer3.cpp: In member function ‘void MPEGaudio::layer3reorderandantialias(int, int, REAL (*)[18], REAL (*)[18])’:
audio/mpeglayer3.cpp:1357: warning: array subscript is above array bounds
audio/mpeglayer3.cpp:1359: warning: array subscript is above array bounds