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doc: Additional information about timeline ID hexadecimal format

Timeline IDs are sometimes presented to the user in hexadecimal format(for example in WAL file names). Add a few bits of information toclarify this.Author: Sébastien Lardière <sebastien@lardiere.net>Discussion:https://www.postgresql.org/message-id/flat/8fef346e-2541-76c3-d768-6536ae052993@lardiere.net

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`@@ -1309,7 +1309,16 @@ restore_command = 'cp /mnt/server/archivedir/%f %p'`
`1309`	`1309`	`a new timeline is created to identify the series of WAL records`
`1310`	`1310`	`generated after that recovery. The timeline`
`1311`	`1311`	`ID number is part of WAL segment file names so a new timeline does`
`1312`		`- not overwrite the WAL data generated by previous timelines. It is`
	`1312`	`+ not overwrite the WAL data generated by previous timelines.`
	`1313`	`+ For example, in the WAL file name`
	`1314`	`+ <filename>0000000100001234000055CD</filename>, the leading`
	`1315`	`+ <literal>00000001</literal> is the timeline ID in hexadecimal. (Note that`
	`1316`	`+ in other contexts, such as server log messages, timeline IDs are`
	`1317`	`+ usually printed in decimal.)`
	`1318`	`+ </para>`
	`1319`	`+`
	`1320`	`+ <para>`
	`1321`	`+ It is`
`1313`	`1322`	`in fact possible to archive many different timelines. While that might`
`1314`	`1323`	`seem like a useless feature, it's often a lifesaver. Consider the`
`1315`	`1324`	`situation where you aren't quite sure what point-in-time to recover to,`

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`@@ -4113,6 +4113,14 @@ restore_command = 'copy "C:\\server\\archivedir\\%f" "%p"' # Windows`
`4113`	`4113`	`a standby server. <literal>latest</literal> is the default.`
`4114`	`4114`	`</para>`
`4115`	`4115`
	`4116`	`+ <para>`
	`4117`	`+ To specify a timeline ID in hexadecimal (for example, if extracted`
	`4118`	`+ from a WAL file name or history file), prefix it with a`
	`4119`	`+ <literal>0x</literal>. For instance, if the WAL file name is`
	`4120`	`+ <filename>00000011000000A10000004F</filename>, then the timeline ID is`
	`4121`	`+ <literal>0x11</literal> (or 17 decimal).`
	`4122`	`+ </para>`
	`4123`	`+`
`4116`	`4124`	`<para>`
`4117`	`4125`	`You usually only need to set this parameter`
`4118`	`4126`	`in complex re-recovery situations, where you need to return to`

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