Contribs: update GSM to 1.0.13

(cherry picked from commit ce30867e)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

contrib/src/gsm/SHA512SUMS

-88d251603c6172ce5cbc07e38d61d981b86e34fa2b1610a47f999a6ecb6db9f3bf5b6205abd8cb66ee70a6f5c6ea5679417582e78b595e081b471b15e7ff471d  gsm-1.0.12.tar.gz
+0d0cf9e1e81e64cd84f588c1e4f0cb74b849d45e41fdebf860f63588084c73c7c5198bfe73a6c976bda5735ee516661d3db00afbb5cc5886a7ee3a7b31d673aa  libgsm_1.0.13.tar.gz

contrib/src/gsm/rules.mak

 # GSM
-GSM_VERSION := 1.0.12
-GSM_URL := $(CONTRIB_VIDEOLAN)/gsm-$(GSM_VERSION).tar.gz
+GSM_VERSION := 1.0.13
+GSM_URL := $(CONTRIB_VIDEOLAN)/libgsm_$(GSM_VERSION).tar.gz
 
-$(TARBALLS)/gsm-$(GSM_VERSION).tar.gz:
+$(TARBALLS)/libgsm_$(GSM_VERSION).tar.gz:
 	$(call download,$(GSM_URL))
 
-.sum-gsm: gsm-$(GSM_VERSION).tar.gz
+.sum-gsm: libgsm_$(GSM_VERSION).tar.gz
 
-gsm: gsm-$(GSM_VERSION).tar.gz .sum-gsm
+gsm: libgsm_$(GSM_VERSION).tar.gz .sum-gsm
 	$(UNPACK)
-	mv gsm-1.0-* gsm-$(GSM_VERSION)
+	mv gsm-1.0-* libgsm_$(GSM_VERSION)
 	$(APPLY) $(SRC)/gsm/gsm-cross.patch
 	$(MOVE)
 ifdef HAVE_MACOSX