Make include-what-you-use happy with some files in source/tools/atlas
and fix what needs to be fixed.
Define ATLASDLLIMPEXP in a regular header instead of a PCH header and
dedupe its definition.
wxWidgets uses WX_ATTRIBUTE_PRINTF this days, so remove the workaround
for ATTRIBUTE_PRINTF.
Ref: #8086
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>