Call init_os_extras() on z/OS

The previous commit added a file and functions for specially dealing
with z/OS.  This commit actually calls the start up one.

Author: IgorTodorovskiIBM

perl.c

@@ -2597,7 +2597,7 @@ S_parse_body(pTHX_ char **env, XSINIT_t xsinit)
 
     if (xsinit)
         (*xsinit)(aTHX);	/* in case linked C routines want magical variables */
-#if defined(VMS) || defined(WIN32) || defined(__CYGWIN__)
+#if defined(VMS) || defined(WIN32) || defined(__CYGWIN__) || defined(__MVS__)
     init_os_extras();
 #endif
 

perl.h

@@ -4469,7 +4469,7 @@ intrinsic function, see its documents for more details.
             cBOOL(PerlLIO_setmode(fileno(fp), mode) != -1)
 #endif
 
-#ifdef __CYGWIN__
+#if defined(__CYGWIN__) || defined(__MVS__)
 void init_os_extras(void);
 #endif