change to readline callback signal handling; fix message when popping shell function context; handle new terminating signals inside terminating signal handler; fix to pattern substitution with null replacement and null string; fix to alias expansion when we get a SIGINT while entering a command substitution in an interactive shell

parser.h

@@ -50,6 +50,7 @@
 #define PST_ENDALIAS	0x200000	/* just finished expanding and consuming an alias */
 #define PST_NOEXPAND	0x400000	/* don't expand anything in read_token_word; for command substitution */
 #define PST_NOERROR	0x800000	/* don't print error messages in yyerror */
+#define PST_STRING	0x1000000	/* parsing a string to a command or word list */
 
 /* Definition of the delimiter stack.  Needed by parse.y and bashhist.c. */
 struct dstack {