Compiler fixes for gcc 10

This patch fixes a few compile warnings/errors that now occur when using gcc
10+.

Also, the Makefile.rules check to turn off partial inlining in gcc versions
greater or equal to 8.2.1 had a bug where it only it only checked against
versions with at least 3 numbers (ex: 8.2.1 vs 10). This patch now ensures
any version above the specified version is correctly compared.

Change-Id: I54718496eb0c3ce5bd6d427cd279a29e8d2825f9

include/asterisk/app.h

@@ -1231,11 +1231,14 @@ int ast_app_group_list_unlock(void);
   \note This defines a structure type, but does not declare an instance
   of the structure. That must be done separately.
  */
+
 #define AST_DEFINE_APP_ARGS_TYPE(type, arglist) \
 	struct type { \
 		unsigned int argc; \
-		char *argv[0]; \
-		arglist \
+		union { \
+			char *argv[sizeof(struct {arglist}) / sizeof(char *)]; \
+			struct {arglist}; \
+		}; \
 	}
 
 /*!