Remove trailing whitespace and untabify
Fix warnings

fix The following warnings.

auto-complete-clang-async.el:37:1:Warning: cl package required at
runtime

auto-complete-clang-async.el:69:4:Warning: misplaced interactive spec:
    `(interactive)'

In ac-clang-handle-error:
auto-complete-clang-async.el:49:26:Warning: reference to free variable
    `ac-clang-executable'

In ac-clang-call-process:
auto-complete-clang-async.el:53:25:Warning: reference to free variable
    `ac-clang-executable'
fixed conflicts for merging