Silence compiler warnings about overrunning sprintf buffers.
Silence compiler warnings about overrunning sprintf buffers.

With GCC 8:

fileam.c: In function ‘external_set_env_vars_ext’:
fileam.c:2315:41: warning: ‘%d’ directive writing between 1 and 10 bytes into a region of size 8 [-Wformat-overflow=]
  sprintf(extvar->GP_LINE_DELIM_LENGTH, "%d", line_delim_len);
                                         ^~
fileam.c:2315:40: note: directive argument in the range [-1, 2147483647]
  sprintf(extvar->GP_LINE_DELIM_LENGTH, "%d", line_delim_len);
                                        ^~~~
fileam.c:2315:2: note: ‘sprintf’ output between 2 and 11 bytes into a destination of size 8
  sprintf(extvar->GP_LINE_DELIM_LENGTH, "%d", line_delim_len);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

For some reason, the compiler is only warning about GP_LINE_DELIM_LENGTH,
and not the other small buffers used similarly. Perhaps because it
considers it OK to overflow to another char[] field in a struct, but not
over a pointer? But for consistency, fix them all.

greenplum-db/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,lisakowen/gpdb,50wu/gpdb,ashwinstar/gpdb,adam8157/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,lisakowen/gpdb,xinzweb/gpdb,ashwinstar/gpdb,lisakowen/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,greenplum-db/gpdb,50wu/gpdb,lisakowen/gpdb,greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,adam8157/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,jmcatamney/gpdb,adam8157/gpdb,lisakowen/gpdb,ashwinstar/gpdb,jmcatamney/gpdb,50wu/gpdb,ashwinstar/gpdb,50wu/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,50wu/gpdb,xinzweb/gpdb,jmcatamney/gpdb,xinzweb/gpdb,xinzweb/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,ashwinstar/gpdb,adam8157/gpdb