Move the fetch and store pixel functions to qdrawhelper.cpp

Move the fetch and store pixel functions to qdrawhelper.cpp

These functions have begun showing in the tst_symbols unit test as
"symbol does not start with q". Since they're never called directly,
they're never inlined. Since they were inline, the compiler was probably
deciding to not export them.

Something changed and it could be anything (new compiler version, new
options, etc.). So mark them static.

Change-Id: I838dfc94edd7f09c202743bff0daf9d20c10c3a6
Reviewed-by: Lars Knoll <lars.knoll@digia.com>