Update .gitignore with auto-generated lex/yacc outputs

Signed-off-by: Jens Axboe <axboe@fb.com>
exp: set float output for int modulus

Signed-off-by: Jens Axboe <axboe@fb.com>
Wire up exp/test-expression-parser

Signed-off-by: Jens Axboe <axboe@fb.com>
Makefile: silence fixup

Signed-off-by: Jens Axboe <axboe@fb.com>