testsuite: Don't include multiline patterns in the the pass/fail log

I see overlong lines in the output when a test fails, for
example for a bug exposed for cris-elf and pru-elf in
gcc.dg/analyzer/allocation-size-multiline-3.c:

Running /x/gcc/testsuite/gcc.dg/analyzer/analyzer.exp ...
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c expected multiline pattern lines 16-25 not found: "\s*int32_t \*ptr = alloca \(99\);[^\n\r]*\n                  \^~~~~~\n  'test_constant_99': events 1-2[^\n\r]*\n    \|[^\n\r]*\n    \|   int32_t \*ptr = alloca \(99\);[^\n\r]*\n    \|                  \^~~~~~\n    \|                  \|[^\n\r]*\n    \|                  \(1\) allocated 99 bytes here[^\n\r]*\n    \|                  \(2\) assigned to 'int32_t \*' \{aka 'int \*'\} here; 'sizeof \(int32_t \{aka int\}\)' is '4'[^\n\r]*\n    \|[^\n\r]*\n"
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c expected multiline pattern lines 34-43 not found: "   int32_t \*ptr = alloca \(n \* 2\);[^\n\r]*\n                  \^~~~~~\n  'test_symbolic': events 1-2[^\n\r]*\n    \|[^\n\r]*\n    \|   int32_t \*ptr = alloca \(n \* 2\);[^\n\r]*\n    \|                  \^~~~~~\n    \|                  \|[^\n\r]*\n    \|                  \(1\) allocated 'n \* 2' bytes here[^\n\r]*\n    \|                  \(2\) assigned to 'int32_t \*' \{aka 'int \*'\} here; 'sizeof \(int32_t \{aka int\}\)' is '4'[^\n\r]*\n    \|[^\n\r]*\n"
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c (test for excess errors)

That multiline-pattern-quoted-on-a-single-line is redundant
when also outputting "lines 16-25" and "lines 34-43".  It's
also so noisy that it can be mistaken for a testsuite error.
If there's a need to inspect it, it can be seen at
verbose-level 4, i.e. persons interested in seeing it
without editing sources can just add "-v -v -v -v".

Let's "prune" the pattern from regular output, instead producing:
Running /x/gcc/testsuite/gcc.dg/analyzer/analyzer.exp ...
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c expected multiline pattern lines 16-25 not found
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c expected multiline pattern lines 34-43 not found
FAIL: gcc.dg/analyzer/allocation-size-multiline-3.c (test for excess errors)

	* lib/multiline.exp (handle-multiline-outputs): Don't include the
	quoted multiline pattern in the pass/fail output.