Update coreSNTP submodule and coreSNTP demo (#631)

Update the coreSNTP submodule to the latest commit. Also, make updates to the coreSNTP demo for the new changes in the SNTP library which include the following:

1. Update to the type for packet size from size_t to uint16_t for parameters in the transport and authentication interfaces.
2. Change in the call to Sntp_SendTimeRequest API to pass the new blockTimeMs parameter added to the API.
3. Update to the clock-offfset type from int32_t to int64_t for representing information in milliseconds. To accommodate this update in the SntpSetTime_t interface, the mathematical model for representing system clock has been updated to store slew rate as milliseconds/second (instead of second/second). This change improves the accuracy of the WinSim demo time correction (because the milliseconds of time difference between server and client time is corrected over the entire polling interval which makes a significant difference!).

This PR also adds demo config macros for setting the block time values passed to the Sntp_SendTimeRequest and Sntp_ReceiveTimeResponse APIs.

lexicon.txt

@@ -162,9 +162,9 @@ busfault
 buttonisr
 bvic
 bytesreceived
-bytesreceived 
+bytesreceived
+bytessent
 bytessent
-bytessent 
 bytestorecv
 bytestosend
 bytestring
@@ -243,6 +243,7 @@ cliprocesscommand
 clk
 clkdiv
 clksel
+clockoffsetms
 clocksource
 closesession
 cmac
@@ -792,6 +793,7 @@ gmon
 gnd
 gnuc
 googleapis
+gov
 gpio
 gpioa
 gpiob
@@ -1010,6 +1012,7 @@ js
 json
 jtag
 jtvic
+june
 juse
 katy
 kbhit
@@ -1044,6 +1047,7 @@ ldi
 ldo
 ldr
 le
+leapsecondinfo
 ledflash
 ledio
 leds
@@ -1297,6 +1301,7 @@ networkcredentials
 nextjobexecutionchanged
 nic
 nirq
+nist
 nmemb
 nmi
 nnnn
@@ -1547,6 +1552,7 @@ pllon
 plls
 pm
 pmc
+pml
 pmp
 pmqttagentcontext
 pmsg
@@ -1824,6 +1830,7 @@ pscheckvariable
 psel
 pserver
 pserverinfo
+pservertime
 psignature
 psl
 pslotlist