Double-quoted term syntax bug

[pmoura]

After this mention in StackOverflow, I run the latest Logtalk tests, that confirm and expose other compliance issues with double-quoted term syntax:

$ logtalk_tester -p tau
% Batch testing started @ 2022-09-08 16:51:02
%         Logtalk version: 3.58.0-b02
%         Tau Prolog version: 0.3.4
%
% Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms
%         20 tests: 0 skipped, 15 passed, 5 failed (0 flaky)
%         completed tests from object tests in 1943 seconds
%         clause coverage n/a
%
% Compilation errors/warnings and failed unit tests
% (compilation errors/warnings might be expected depending on the test)
!     lgt_double_quoted_term_13: failure (in 0.0029999999999998916 seconds)
!       test goal succeeded but should have thrown an error:
!         expected error(syntax_error(A),B)
!       in file Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt between lines 98-104
!     lgt_double_quoted_term_14: failure (in 0.002000000000000224 seconds)
!       test goal succeeded but should have thrown an error:
!         expected error(syntax_error(A),B)
!       in file Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt between lines 104-108
!     lgt_double_quoted_term_15: failure (in 0.0009999999999998899 seconds)
!       test goal throws an error but should have succeeded: error(syntax_error('token not found'),[line(1),column(10),token_not_found])
!       in file Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt between lines 108-115
!     lgt_double_quoted_term_16: failure (in 0.0 seconds)
!       test goal throws an error but should have succeeded: error(syntax_error('token not found'),[line(1),column(10),token_not_found])
!       in file Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt between lines 115-120
!     lgt_double_quoted_term_17: failure (in 0.0 seconds)
!       test goal throws an error but should have succeeded: error(syntax_error('token not found'),[line(1),column(10),token_not_found])
!       in file Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt between lines 120-125
%
% Failed tests
Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt - lgt_double_quoted_term_13 @ tests
Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt - lgt_double_quoted_term_14 @ tests
Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt - lgt_double_quoted_term_15 @ tests
Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt - lgt_double_quoted_term_16 @ tests
Documents/Logtalk/logtalk3/tests/prolog/syntax/double_quoted_terms/tests.lgt - lgt_double_quoted_term_17 @ tests
%
% 1 test sets: 1 completed, 0 skipped, 0 broken, 0 timedout, 0 crashed
% 20 tests: 0 skipped, 15 passed, 5 failed (0 flaky)
%
% Batch testing ended @ 2022-09-08 17:26:16