Fixed code that caused a seg-fault after parsing a (deferred) post-count argument followed by a (nested) function-call argument.

The old broken code defers the count until the end of the (parent function's) argument list.  But, a nested function call clears the pointer to the deferred type.  That leads to an access violation.
The new code defers only until the end of each argument.  Fixes #1320.

test/val/bug1320.c

@@ -0,0 +1,44 @@
+/*
+  Copyright 2020, The cc65 Authors
+
+  This software is provided "as-is", without any express or implied
+  warranty. In no event will the authors be held liable for any damages
+  arising from the use of this software.
+
+  Permission is granted to anyone to use this software for any purpose,
+  including commercial applications; and, to alter it and redistribute it
+  freely, subject to the following restrictions:
+
+  1. The origin of this software must not be misrepresented; you must not
+     claim that you wrote the original software. If you use this software
+     in a product, an acknowledgment in the product documentation would be
+     appreciated, but is not required.
+  2. Altered source versions must be plainly marked as such, and must not be
+     misrepresented as being the original software.
+  3. This notice may not be removed or altered from any source distribution.
+*/
+
+/*
+  Test of a post-counted pointer argument,
+  followed by a (nested) function-call argument.
+  Test that compiling it doesn't cause a seg-fault.
+
+  https://github.com/cc65/cc65/issues/1320
+*/
+
+static char *var;
+
+static void foo (char *, char)
+{
+}
+
+static char bar (void)
+{
+    return 'b';
+}
+
+int main (void)
+{
+    foo (var++, bar ());
+    return 0;
+}