Fix for log_line_prefix and session display

Currently, our session id, displayed by log_line_prefix and CSV output,
is made up of the session start time epoch seconds and the process id.
The problem is that the printf mask is currently %lx.%x, causing a
process id less than 4096 to not display a full four hex digits after
the decimal point. I think this is confusing because the number .423
appears higher than .1423, though it is not. Here is what our current
output looks like with log_line_prefix="%c: ":

50785b3e.7ff9: ERROR: syntax error at or near "test" at character 1
50785b3e.7ff9: STATEMENT: test
50785b3e.144: ERROR: syntax error at or near "test" at character 1
50785b3e.144: STATEMENT: test

With my fix, here is the updated output:

507864d3.7ff2: ERROR: syntax error at or near "test" at character 1
507864d3.7ff2: STATEMENT: test
507864d3.013d: ERROR: syntax error at or near "test" at character 1
507864d3.013d: STATEMENT: test

Patch attached.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +