Back out changes in #366 and introduce read_argv_int/float()

* Revert "Extend "read_argv" native"

This reverts commit aaa2934595.

This broke binary compatibility with either older, already compiled
plugins, or newly compiled plugins if you forgot to update .inc headers.

This happened because read_argv used to receive maxlen by value, and
after
this commit it receives it by reference. This causes read_argv either
to fail, or worse, to buffer overflow, resulting in a security vulnerability.

Newly introduced functionality for read_argv should be added with a new,
separate native.

* Add "read_argv_int" & "read_argv_float" natives

plugins/include/amxmodx.inc

@@ -1318,32 +1318,39 @@ native get_playersnum(flag = 0);
 native get_players(players[MAX_PLAYERS], &num, const flags[] = "", const team[] = "");
 
 /**
- * Retrieves argument of client command.
+ * Retrieves argument of client command as string.
  *
  * @note Should only be used inside of the client_command() forward.
- * @note Usage examples:
- *       value = read_argv(1);
- *       read_argv(2, floatvalue);
- *       written = read_argv(3, buffer, buffersize);
  *
  * @param id        Argument index starting from 1, 0 returns the command itself
- * @param ...       Changes the native's behavior depending on how many
- *                  additional parameters are provided:
- *                     0 - Return the argument integer value directly
- *                     1 - Store the argument float value in the variable passed
- *                         as the second parameter
- *                     2 - Copy the argument string value to the buffer provided
- *                         in the second parameter, using the third as the
- *                         maximum buffer size
+ * @param output    Buffer to copy command argument to
+ * @param len       Maximum buffer size
  *
- * @return          Changes depending on how many additional parameters are
- *                  provided:
- *                     0 - Returns the argument integer value
- *                     1 - Returns the argument float value, converted
- *                         (truncated) to an integer
- *                     2 - Returns the number of cells written to the buffer
+ * @return          Number of cells written to buffer
  */
-native read_argv(id, any:...);
+native read_argv(id, output[], len);
+
+/**
+ * Retrieves argument of client command as integer value.
+ *
+ * @note Should only be used inside of the client_command() forward.
+ *
+ * @param id        Argument index starting from 1
+ *
+ * @return          Integer value
+ */
+native read_argv_int(id);
+
+/**
+ * Retrieves argument of client command as float value.
+ *
+ * @note Should only be used inside of the client_command() forward.
+ *
+ * @param id        Argument index starting from 1
+ *
+ * @return          Float value
+ */
+native Float:read_argv_float(id);
 
 /**
  * Retrieves full client command string.