patch 9.0.2180: POSIX function name in exarg causes issues

Problem:  POSIX function name in exarg struct causes issues
          on OpenVMS
Solution: Rename getline member in exarg struct to ea_getline,
          remove isinf() workaround for VMS

There are compilers that do not treat well POSIX functions - like
getline - usage in the structs.

Older VMS compilers could digest this... but the newer OpenVMS compilers
( like VSI C x86-64 X7.4-843 (GEM 50XB9) ) cannot deal with these
structs. This could be limited to getline() that is defined via
getdelim() and might not affect all POSIX functions in general - but
avoiding POSIX function names usage in the structs is a "safe side"
practice without compromising the functionality or the code readability.

The previous OpenVMS X86 port used a workaround limiting the compiler
capabilities using __CRTL_VER_OVERRIDE=80400000
In order to make the OpenVMS port future proof, this pull request
proposes a possible solution.

closes: #13704

Signed-off-by: Zoltan Arpadffy <zoltan.arpadffy@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/scriptfile.c b/src/scriptfile.c
index 35582a8..69016bf 100644
--- a/src/scriptfile.c
+++ b/src/scriptfile.c
@@ -2469,7 +2469,7 @@
     int
 sourcing_a_script(exarg_T *eap)
 {
-    return (getline_equal(eap->getline, eap->cookie, getsourceline));
+    return (getline_equal(eap->ea_getline, eap->cookie, getsourceline));
 }
 
 /*
@@ -2497,7 +2497,7 @@
 	name = eap->arg;
 
     // Setup for conversion from the specified encoding to 'encoding'.
-    sp = (source_cookie_T *)getline_cookie(eap->getline, eap->cookie);
+    sp = (source_cookie_T *)getline_cookie(eap->ea_getline, eap->cookie);
     convert_setup(&sp->conv, name, p_enc);
 
     if (name != eap->arg)
@@ -2561,7 +2561,7 @@
     int		idx;
 
     if (reanimate)
-	((source_cookie_T *)getline_cookie(eap->getline,
+	((source_cookie_T *)getline_cookie(eap->ea_getline,
 					      eap->cookie))->finished = FALSE;
 
     // Cleanup (and inactivate) conditionals, but stop when a try conditional
@@ -2575,7 +2575,7 @@
 	report_make_pending(CSTP_FINISH, NULL);
     }
     else
-	((source_cookie_T *)getline_cookie(eap->getline,
+	((source_cookie_T *)getline_cookie(eap->ea_getline,
 					       eap->cookie))->finished = TRUE;
 }