Work around MinGW GCC version >=4.5 always_inline+dllexport bug.

Use regular inline instead of always_inline for MinGW GCC build. GCC 4.5
and later spit out an error on always_inline dllexport functions, which
breaks the build for these versions of GCC (see bug 5938).

Change-Id: I444380ff98071b4653a91d074494ace579b4a622
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>
(cherry picked from commit 310b446a81dd927739e503b03389641f1aa13ab4)
Sanity-Review: Qt Sanity Bot <qt_sanity_bot@ovi.com>