fix: saturate eSBR QMF synthesis output - #134
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ixheaacd_esbr_qmfsyn64_winadd() and ixheaacd_esbr_qmfsyn32_winadd() in the generic C and ARMv7 paths cast (syn_out >> 31) straight to WORD32. The WORD64 accumulator can exceed WORD32 range on a full-scale sample, so the cast wraps it to a negative spike instead of clipping - audible as crackling / overdrive on loud material. The ARMv8 64-band implementation already does the saturating narrowing with ixheaac_sat64_32(). Apply the same to the generic C, ARMv7 C and ARMv8 32-band variants, and use VQSHRN.S64 instead of VSHRN.S64 in the ARMv7 assembly.
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sample_buffer[ch_fac*k] = (WORD32)(syn_out >> 31) wraps on full-scale samples (syn_out>>31 exceeds 2^31), giving a negative spike instead of clipping.
ARMv8 64-band already uses ixheaac_sat64_32(); the rest don't.
Found decoding a full-scale HE-AAC stream on x86_64; matches ffmpeg/faad after.