Replace getprogname() to argv[0] in bnaddsub

[Kinichiro Inoguchi]

To run regress bnaddsub on Windows, I would like to supersede getprogname
with argv[0] since it is not on Windows.

OK ?

Index: regress/lib/libcrypto/bn/addsub/bnaddsub.c
===================================================================
RCS file: /cvs/src/regress/lib/libcrypto/bn/addsub/bnaddsub.c,v
retrieving revision 1.1
diff -u -p -u -p -r1.1 bnaddsub.c
--- regress/lib/libcrypto/bn/addsub/bnaddsub.c  10 Jul 2018 16:57:50 -0000      
1.1
+++ regress/lib/libcrypto/bn/addsub/bnaddsub.c  17 Jul 2018 13:01:08 -0000
@@ -216,7 +216,7 @@ main(int argc, char *argv[])
 
        if ((bio_err = BIO_new_fp(stderr, BIO_NOCLOSE)) == NULL) {
                fprintf(stderr, "%s: failed to initialize bio_err",
-                   getprogname());
+                   argv[0]);
                return 1;
        }