Always disable loplugin:expressionalwayszero, to avoid false positives

bdade7e3fc "tdf#105444 DOCX import: don't put
extra paragraphs in comments" caused

> /home/sbergman/lo2/core/writerfilter/source/dmapper/DomainMapper_Impl.cxx:441:22: error: expression always evaluates to zero, lhs=0 rhs=unknown [loplugin:expressionalwayszero]
>                     (sizeof(SAL_NEWLINE_STRING)-1 == 2 && xCursor->getString() == "\n"))
>                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

now with sufficiently new Clang, and the code looks reasonable, and there's no
apparent way to avoid such false positives in the plugin.  (It could check for a
sub-expression of the problematic expression being an object-like macro, but
SAL_NEWLINE_STRING could just as well be a variable instead of a macro.  That
variable would need to be defined in some #if to have different values on
different platforms, so the plugin could theoretically check for such
conditional inclusion, but it's not clear whether that's worth it and would even
be a useful heuristic to not produce neither too many false positives nor too
many false negatives.)  So just disable the plugin for good.

Change-Id: I85dc8573735ccac4e19be20ab7443cbaa85a3164
Reviewed-on: https://gerrit.libreoffice.org/60907
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/expressionalwayszero.cxx

@@ -150,12 +150,7 @@ bool ExpressionAlwaysZero::TraverseStaticAssertDecl( StaticAssertDecl * )
     return true;
 }
 
-// on clang-3.8, this plugin can generate OOM
-#if CLANG_VERSION >= 30900
-loplugin::Plugin::Registration< ExpressionAlwaysZero > X("expressionalwayszero");
-#else
 loplugin::Plugin::Registration< ExpressionAlwaysZero > X("expressionalwayszero", false);
-#endif
 
 }