Define a constant for function-not-found in input.cpp

Avoids differences in widths of wchar_t, hopefully addressing
issue #2284

src/builtin_commandline.cpp

@@ -455,7 +455,7 @@ static int builtin_commandline(parser_t &parser, wchar_t **argv)
         for (i=w.woptind; i<argc; i++)
         {
             wchar_t c = input_function_get_code(argv[i]);
-            if (c != (wchar_t)(-1))
+            if (c != INPUT_CODE_NONE)
             {
                 /*
                   input_unreadch inserts the specified keypress or

src/input.cpp

@@ -557,7 +557,7 @@ static void input_mapping_execute(const input_mapping_t &m, bool allow_commands)
 
     for (wcstring_list_t::const_iterator it = m.commands.begin(), end = m.commands.end(); it != end; ++it)
     {
-        if (input_function_get_code(*it) != -1)
+        if (input_function_get_code(*it) != INPUT_CODE_NONE)
             has_functions = true;
         else
             has_commands = true;
@@ -1103,14 +1103,12 @@ wcstring_list_t input_function_get_names(void)
 
 wchar_t input_function_get_code(const wcstring &name)
 {
-
-    size_t i;
-    for (i = 0; i<(sizeof(code_arr)/sizeof(wchar_t)) ; i++)
+    for (size_t i=0; i < sizeof code_arr / sizeof *code_arr; i++)
     {
         if (name == name_arr[i])
         {
             return code_arr[i];
         }
     }
-    return -1;
+    return INPUT_CODE_NONE;
 }

src/input.h

@@ -194,6 +194,7 @@ bool input_terminfo_get_name(const wcstring &seq, wcstring *out_name);
 wcstring_list_t input_terminfo_get_names(bool skip_null);
 
 /** Returns the input function code for the given input function name. */
+#define INPUT_CODE_NONE (wchar_t(-1))
 wchar_t input_function_get_code(const wcstring &name);
 
 /** Returns a list of all existing input function names */