[telnet|rlogin]_gate now returns bool (false if failed to connect)

Previously, there was no real way to tell if the call to telnet_gate() or rlogin_gate() was successful (e.g. to display or an error message to the user), though there were error/warning messages logged for the sysop. Equivalent JS bbs object methods now return Boolean too.

Include ":port" part of address argument to bbs.[telnet|rlogin]_gate methods in JSDOCS.

Removed a bunch of extraneous (copy-pasted?) JS_SET_RVAL() calls from js_bbs.cpp. This just makes the code a little easier to grok.