Optimize sys_vars.sysvar_* tests

<serg> in 10.1 there are now sys_vars.sysvar_* tests they list all system variables and their metadata
<serg> this is, obviously, pretty fragile, I've split them in debug/non-debug, embedded, and created rdiffs for xtradb/innodb, 64bit/32bit, etc
<serg> and simply disabled some of them for valgrind or non-debug builds
<serg> still they require a lot of maintenance. Like after bug changes I need to build 32-bit version to update 32-bit rdiffs, and often do the same on windows etc
<serg> I wonder whether you can manage to optimize them somehow (what should rdiff, what should be .result, where they should be simply disabled, etc)
<serg> so that they won't break that often or that rdiffs apply cleanly?
<serg> like mysqld--help test, rdiff for windows almost always just works, it's enough to update the result on linux
<serg> that's not particularly urgent, I'll keep updating tests manually anyway
<serg> but I've spent too much time on it already and mostly out of ideas now
<serg> that's one of the new features in 10.1 that I've recently pushed
<serg> INFORMATION_SCHEMA.SYSTEM_VARIABLES table: https://mariadb.com/kb/eninformation-schema-system_variables-table/
<elenst> Do you expect it to be so useful that it's worth the trouble?
<serg> the feature - yes, absolutely. tests? I don't know, really, perhaps disabling them isn't that bad
<serg> I'd like to have this feature tested, but it doesn't need to list all variables, I agree