gcrypt: use vlc_global_mutex
gcrypt: use vlc_global_mutex

This saves a few mutexes, but it does not really solve gcrypt
reentrancy. gcry_control() should only be called once for all per copy
of gcrypt in the memory. This is hard to conciliate with dlopen().

shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc,xkfz007/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.1,krichter722/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc,xkfz007/vlc,vlc-mirror/vlc,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,shyamalschandra/vlc,krichter722/vlc,krichter722/vlc,shyamalschandra/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.2