diagnostics: Fix sporadic test failure

diagnostics: Fix sporadic test failure

it turns out to be reproducible this way:

COLUMNS=80 make check-gcc-c RUNTESTFLAGS="plugin.exp=diagnostic*"

Running /home/ed/gnu/gcc-trunk/gcc/testsuite/gcc.dg/plugin/plugin.exp ...
FAIL: gcc.dg/plugin/diagnostic-test-expressions-1.c
 -fplugin=./diagnostic_plugin_test_tree_expression_range.so  1 blank line(s) in output
FAIL: gcc.dg/plugin/diagnostic-test-expressions-1.c
 -fplugin=./diagnostic_plugin_test_tree_expression_range.so  expected multiline pattern lines 550-551 not found: "                            __builtin_types_compatible_p \(long, int\) \+ f \(i\)\);.*\n                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\^~~~~~~\n"
FAIL: gcc.dg/plugin/diagnostic-test-expressions-1.c
 -fplugin=./diagnostic_plugin_test_tree_expression_range.so (test for excess errors)

a lot more errors happen with COLUMNS=20.

2021-05-29  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	* gcc.dg/plugin/diagnostic_plugin_show_trees.c (plugin_init): Fix caret_max_with.
	* gcc.dg/plugin/diagnostic_plugin_test_inlining.c
	(plugin_init): Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_paths.c (plugin_init): Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_string_literals.c
	(plugin_init): Likewise.
	* gcc.dg/plugin/diagnostic_plugin_test_tree_expression_range.c
	(plugin_init): Likewise.