company--multi-backend-adapter-candidates: compare string values of prefix

Fixes #112
company-clang--build-complete-args: don't call -cc1 directly

#111
company-clang--annotation: include method qualifiers in the annotation

Fixes #113
NEWS: document the change in clang invocation
company--continue: don't pass the new prefix to `company-cancel'

Closes #118
company-files-complete: move files in subdirs to the end

#116
Introduce company-tooltip-flip-when-above

Closes #116
Fix typo
extended gtags functionality #90
showing annotations and meta