audiosystem: Fix coding style warning.

./audiosystem/audiosystem_instance.cc:52:  Missing spaces around = [whitespace/operators] [4]
filesystem: Include <tuple> when using it.

./filesystem/filesystem_instance.h:85:  Add #include <tuple> for tuple<> [build/include_what_you_use] [4]
system_info: Fix coding style warnings.

./system_info/system_info_instance.cc:90:  Missing spaces around =  [whitespace/operators] [4]
./system_info/system_info_instance.cc:111:  Missing spaces around =  [whitespace/operators] [4]
./system_info/system_info_instance.cc:120:  Missing spaces around =  [whitespace/operators] [4]
Merge pull request #412 from rakuco/fix-style-issues

Fix coding style warnings.