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'
Allow the location of "llvm-config" to be overridden on the "make" command line.

This commit adds an LLVM_CONFIG variable to the Makefile, and uses it rather
than directly referencing llvm-config. This allows the value to be changed on
the make command line. For example, on my system where I have installed the llvm
snapshot package for debian, I am running "make LLVM_CONFIG=llvm-config-3.4".

This commit adds a footnote to the README file to document this possibility.
Don't call llvm-config twice when setting LDLIBS.

llvm-config was being called twice when setting LDLIBS: once to get --ldflags,
and another time for "--libs all". It turns out that nothing in "--libs all" is
actually required, so drop that invocation.

Also dropped libstdc++ while I was here, that is not required either.
Specify C99 when building.

I'm seeing complaints about
"warning: ISO C90 does not support ‘long long’ [-Wlong-long]"
when building with GCC 4.7.2, libclang 3.4ish built from r182715.

This commit silences those warnings by telling GCC to build in C99 mode.
Make snippet expansion occur for non-overloaded functions.

Snippet expansion happens when auto-complete performs the action associated with
completing a function's argument list. If a function only has one possible
argument list, auto-complete will expand the it as part of expanding the common
part of the possible completions. Since there is no user interaction in this
case, auto-complete does not call the associated "action" (which would perform
snippet expansion).

As of this commit, when we know there is only one possible argument list, we
call the action ourselves to get snippet expansion to occur.

This fixes Golevka/emacs-clang-complete-async#32.