Fix previous commit's ecpg_clocale for ppc Darwin.

Per buildfarm member prairiedog, this platform rejects uninitialized
global variables in shared libraries.  Back-patch to v10, like the
addition of the variable.

Reviewed by Tom Lane.

Discussion: https://postgr.es/m/20220703030619.GB2378460@rfd.leadboat.com

src/interfaces/ecpg/ecpglib/connect.c

@@ -11,7 +11,7 @@
 #include "sqlca.h"
 
 #ifdef HAVE_USELOCALE
-locale_t	ecpg_clocale;
+locale_t	ecpg_clocale = (locale_t) 0;
 #endif
 
 #ifdef ENABLE_THREAD_SAFETY