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/vim9compile.c b/src/vim9compile.c
index 7bf2552..b896f43 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -971,7 +971,7 @@
     void
 fill_exarg_from_cctx(exarg_T *eap, cctx_T *cctx)
 {
-    eap->getline = exarg_getline;
+    eap->ea_getline = exarg_getline;
     eap->cookie = cctx;
     eap->skip = cctx->ctx_skip == SKIP_YES;
 }
@@ -2628,7 +2628,7 @@
 	list_T	   *l;
 
 	// [let] varname =<< [trim] {end}
-	eap->getline = exarg_getline;
+	eap->ea_getline = exarg_getline;
 	eap->cookie = cctx;
 	l = heredoc_get(eap, op + 3, FALSE, TRUE);
 	if (l == NULL)