Description:
------------
PHP sends the following string to Net-SNMP to parse as an address:

"udp6:fc00::23:250:56ff:fe82:3177"

Net-SNMP understands the final part of the IP address to be a port number, since 
it has no hexadecimal characters in it.  There was an earlier bug filed and 
fixed in PHP 5.4 that involved IPv6 but that fix only partially addressed the 
issue (bug #42918).  It made PHP correctly parse IPv6 address but it didn't 
ensure that PHP sent Net-SNMP a form of address that it will always correctly 
interpret.

My patch causes square brackets to always surround the IPv6 address, so that 
Net-SNMP cannot possibly interpret the last part of the Ipv6 address as a port 
number.  The port number will be placed outside the square brackets.  Here is an 
example of how it will now send the IPV6 address to Net-SNMP:

"udp6:[fc00::23:250:56ff:fe82:3177]"

Or if there is a custom port number 1234:

"udp6:[fc00::23:250:56ff:fe82:3177]:1234"

Net-SNMP will correctly parse that and use the default SNMP port number (161) if 
none is specified or the provided port number otherwise.

I have reproduced this in 5.4.1 and 5.4.14.

Test script:
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$s=new SNMP(SNMP::VERSION_2C, '[fc00::23:250:56ff:fe82:3177]', 'public');
print_r($s->get('.1.3.6.1.2.1.1.1.0'));



Expected result:
----------------
STRING: "Linux mykernel12345 #5 SMP Fri Jun 1 19:44:50 GMT 2012 x86_64"

Actual result:
--------------
Warning: SNMP::get(): No response from udp6:fc00::23:250:56ff:fe82:3177 in php 
shell code on line 1