Remove duplicate user CFLAGS; Automake combines them automatically
Enable GCC warnings in ALSA and MP3 plugins

Warnings not enabled in AAC plugin to avoid warnings from FAAD files
Fix compiler warnings in alsa.c, aac.c, aac_parser.c, and mpgmad.c

Fixed these GCC warnings (x86-64 GCC 4.7 build):

alsa.c:222:5: warning: pointer targets in passing argument 3 of 'snd_pcm_hw_params_set_rate_near' differ in signedness [-Wpointer-sign]
alsa.c:231:5: warning: pointer targets in passing argument 2 of 'snd_pcm_hw_params_get_channels_min' differ in signedness [-Wpointer-sign]
alsa.c:232:5: warning: pointer targets in passing argument 2 of 'snd_pcm_hw_params_get_channels_max' differ in signedness [-Wpointer-sign]
alsa.c:248:5: warning: pointer targets in passing argument 2 of 'snd_pcm_hw_params_get_channels' differ in signedness [-Wpointer-sign]
alsa.c:269:5: warning: enumeration value 'SND_PCM_FORMAT_UNKNOWN' not handled in switch [-Wswitch]
. . .
alsa.c:115:1: warning: label 'retry' defined but not used [-Wunused-label]
alsa.c:632:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
alsa.c:703:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
alsa.c:704:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
alsa.c:93:1: warning: 'palsa_get_channels' declared 'static' but never defined [-Wunused-function]
alsa.c:96:1: warning: 'palsa_get_endianness' declared 'static' but never defined [-Wunused-function]

mpgmad.c:284:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
mpgmad.c:612:21: warning: format '%lld' expects argument of type 'long long int', but argument 5 has type 'int64_t' [-Wformat]
mpgmad.c:654:17: warning: format '%llX' expects argument of type 'long long unsigned int', but argument 6 has type 'int64_t' [-Wformat]
mpgmad.c:684:9: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'int64_t' [-Wformat]
mpgmad.c: In function 'cmp3_set_extra_properties':
mpgmad.c:730:9: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'int64_t' [-Wformat]
mpgmad.c:888:9: warning: format '%f' expects argument of type 'double', but argument 3 has type 'const char *' [-Wformat]
mpgmad.c:1080:30: warning: pointer targets in initialization differ in signedness [-Wpointer-sign]
mpgmad.c:1094:13: warning: pointer targets in passing argument 2 of 'mad_stream_buffer' differ in signedness [-Wpointer-sign]
mpgmad.c:1156:17: warning: unused variable 'readsize' [-Wunused-variable]
mpgmad.c:1232:21: warning: unused variable 'l' [-Wunused-variable]
mpgmad.c:1265:9: warning: format '%d' expects argument of type 'int', but argument 4 has type 'double' [-Wformat]
mpgmad.c:1365:9: warning: pointer targets in passing argument 4 of 'deadbeef->plt_insert_cue_from_buffer' differ in signedness [-Wpointer-sign]

aac.c:123:5: warning: format '%lld' expects argument of type 'long long int', but argument 3 has type 'uint64_t' [-Wformat]
aac.c:123:5: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'uint64_t' [-Wformat]
aac.c:190:58: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
aac.c:227:17: warning: format '%d' expects argument of type 'int', but argument 3 has type 'long unsigned int' [-Wformat]
aac.c:178:9: warning: unused variable 'eof' [-Wunused-variable]
aac.c:267:5: warning: format '%lld' expects argument of type 'long long int', but argument 3 has type 'int64_t' [-Wformat]
aac.c:351:13: warning: format '%lld' expects argument of type 'long long int', but argument 6 has type 'int64_t' [-Wformat]
aac.c:295:13: warning: variable 'sr' set but not used [-Wunused-but-set-variable]
aac.c:683:9: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'int64_t' [-Wformat]
aac.c:692:9: warning: pointer targets in passing argument 2 of 'NeAACDecInit' differ in signedness [-Wpointer-sign]
aac.c:888:13: warning: pointer targets in passing argument 5 of 'mp4ff_read_sample' differ in signedness [-Wpointer-sign]
aac.c:922:17: warning: format '%lld' expects argument of type 'long long int', but argument 3 has type 'int64_t' [-Wformat]
aac.c:932:13: warning: pointer targets in passing argument 3 of 'NeAACDecDecode' differ in signedness [-Wpointer-sign]
aac.c:935:17: warning: format '%d' expects argument of type 'int', but argument 5 has type 'long unsigned int' [-Wformat]
aac.c:991:66: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
aac.c:1008:17: warning: format '%d' expects argument of type 'int', but argument 3 has type 'long unsigned int' [-Wformat]
aac.c:1359:9: warning: format '%lld' expects argument of type 'long long int', but argument 4 has type 'int64_t' [-Wformat]
aac.c:1375:13: warning: pointer targets in passing argument 4 of 'deadbeef->plt_insert_cue_from_buffer' differ in signedness [-Wpointer-sign]
aac.c:1350:9: warning: unused variable 'v1err' [-Wunused-variable]
aac.c:1349:9: warning: unused variable 'v2err' [-Wunused-variable]
aac.c:1348:9: warning: unused variable 'apeerr' [-Wunused-variable]

aac_parser.c:59:17: warning: unused variable 'profiles' [-Wunused-variable]
aac_parser.c:57:9: warning: unused variable 'profile_objecttype' [-Wunused-variable]

Warnings I’m not sure how to fix:

aac.c: In function 'parse_aac_stream':
aac.c:166:13: warning: unused variable 'offs' [-Wunused-variable]
aac.c:180:9: warning: unused variable 'remaining' [-Wunused-variable]
aac.c: In function 'seek_raw_aac':
aac.c:979:9: warning: unused variable 'remaining' [-Wunused-variable]
aac.c:977:9: warning: unused variable 'eof' [-Wunused-variable]
aac.c:975:9: warning: unused variable 'stream_ch' [-Wunused-variable]
aac.c:974:9: warning: unused variable 'stream_sr' [-Wunused-variable]
aac.c:973:9: warning: unused variable 'nsamples' [-Wunused-variable]

aac_parser.c: In function 'aac_sync':
aac_parser.c:98:9: warning: unused variable 'adts_buffer_fullness' [-Wunused-variable]
aac_parser.c:92:9: warning: unused variable 'copyright_ident_start' [-Wunused-variable]
aac_parser.c:91:9: warning: unused variable 'copyright_ident_bit' [-Wunused-variable]
aac_parser.c:90:9: warning: unused variable 'home' [-Wunused-variable]
aac_parser.c:89:9: warning: unused variable 'orig_copy' [-Wunused-variable]
aac_parser.c:81:9: warning: unused variable 'private_bit' [-Wunused-variable]
aac_parser.c:61:9: warning: unused variable 'header_size' [-Wunused-variable]
aac_parser.c:58:9: warning: unused variable 'layer' [-Wunused-variable]
aac_parser.c:56:9: warning: unused variable 'version' [-Wunused-variable]
tracing