Put this in your User JS:
var search = document.getElementsByClassName('catalog_search')[0]
search.innerHTML = search.innerHTML.replace('[', '').replace(']', '').replace('Search', '[Search]')
var showall = search.previousElementSibling
showall.innerHTML = showall.innerHTML.replace('[', '').replace(']', '').replace('Show all', '[Show all]')
The "Show all" button is mysteriously missing from the code in the Github repository, I'd submit a pull request otherwise.