This reverts commit 9f75cc9e.
It breaks usage of G_STRFUNC when compiling applications with
-Wpedantic — __func__ is not #defined, so G_STRFUNC was falling
through to using __FUNCTION__, which raises a warning with
Fixes: #1755 (closed)
Trivial backport of !799 (merged).
This will create a new commit in order to revert the existing changes.