Replaced left shift of negative number with multiplication.

This avoid these issues reported by gcc sanitazion:

 vorbis_1ch_q-0.5_44100.ogg : ../../lib/psy.c:319:23: runtime error: left shift of negative value -4
 #0 0x7f0ed5b9f8f2 in _vp_psy_init ../../lib/psy.c:319
 #1 0x7f0ed5bf295d in _vds_shared_init ../../lib/block.c:225
 #2 0x7f0ed5bf46c1 in vorbis_analysis_init ../../lib/block.c:298
 #3 0x558b2aead6eb in write_vorbis_data_or_die ../../test/write_read.c:61
 #4 0x558b2aeacc39 in main ../../test/test.c:58
 #5 0x7f0ed51a9249 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
 #6 0x7f0ed51a9304 in __libc_start_main_impl ../csu/libc-start.c:360
 #7 0x558b2aead0d0 in _start (test/.libs/test+0x50d0)

 vorbis_1ch_q-0.5_44100.ogg : ../../lib/floor1.c:820:24: runtime error: left shift of negative value -11
 #0 0x7fd25e52a613 in floor1_encode ../../lib/floor1.c:820
 #1 0x7fd25e6130de in mapping0_forward ../../lib/mapping0.c:617
 #2 0x7fd25e59f5b0 in vorbis_analysis ../../lib/analysis.c:46
 #3 0x558ec7bfea21 in write_vorbis_data_or_die ../../test/write_read.c:101
 #4 0x558ec7bfdc39 in main ../../test/test.c:58
 #5 0x7fd25db33249 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
 #6 0x7fd25db33304 in __libc_start_main_impl ../csu/libc-start.c:360
 #7 0x558ec7bfe0d0 in _start (test/.libs/test+0x50d0)