Build: move subtitles codecs to m/codec/ instead of m/codec/subtitles

Most subtitles codecs are still in m/codec/, like dvbsub, svcdsub, cvdsub, libass, spudec.
This makes it consistent.

This also removes an extra folder to compile...

configure.ac

@@ -4567,7 +4567,6 @@ AC_CONFIG_FILES([
   modules/codec/dmo/Makefile
   modules/codec/omxil/Makefile
   modules/codec/shine/Makefile
-  modules/codec/subtitles/Makefile
   modules/codec/spudec/Makefile
   modules/codec/wmafixed/Makefile
   modules/control/Makefile

modules/codec/Modules.am

@@ -1,4 +1,4 @@
-SUBDIRS = dmo avcodec shine subtitles spudec wmafixed omxil
+SUBDIRS = dmo avcodec shine spudec wmafixed omxil
 SOURCES_a52 = a52.c a52.h
 SOURCES_dts = dts.c
 SOURCES_flac = flac.c
@@ -34,6 +34,9 @@ SOURCES_kate = kate.c
 SOURCES_schroedinger = schroedinger.c
 SOURCES_libass = libass.c
 SOURCES_aes3 = aes3.c
+SOURCES_subsdec = subsass.c subsdec.c subsdec.h
+SOURCES_subsusf = subsusf.c subsdec.h
+SOURCES_t140 = t140.c
 
 libvlc_LTLIBRARIES += \
 	liba52_plugin.la \
@@ -50,4 +53,7 @@ libvlc_LTLIBRARIES += \
 	librawvideo_plugin.la \
 	libsvcdsub_plugin.la \
 	libinvmem_plugin.la \
+	libsubsdec_plugin.la \
+	libsubsusf_plugin.la \
+	libt140_plugin.la \
 	$(NULL)

modules/codec/subtitles/Modules.am

@@ -1,9 +0,0 @@
-SOURCES_subsdec = subsass.c subsdec.c subsdec.h
-SOURCES_subsusf = subsusf.c subsdec.h
-SOURCES_t140 = t140.c
-
-libvlc_LTLIBRARIES += \
-	libsubsdec_plugin.la \
-	libsubsusf_plugin.la \
-	libt140_plugin.la \
-	$(NULL)

po/POTFILES.in

@@ -394,11 +394,11 @@ modules/codec/speex.c
 modules/codec/spudec/parse.c
 modules/codec/spudec/spudec.c
 modules/codec/spudec/spudec.h
-modules/codec/subtitles/subsass.c
-modules/codec/subtitles/subsdec.c
-modules/codec/subtitles/subsdec.h
-modules/codec/subtitles/subsusf.c
-modules/codec/subtitles/t140.c
+modules/codec/subsass.c
+modules/codec/subsdec.c
+modules/codec/subsdec.h
+modules/codec/subsusf.c
+modules/codec/t140.c
 modules/codec/svcdsub.c
 modules/codec/telx.c
 modules/codec/theora.c