- Always include config.h before Imlib2.h
Needed for X_DISPLAY_MISSING.
- Always include config.h and Imlib2.h first
Should make it more likely to spot stuff missing but required
in Imlib2.h, like stddef.h.
gtest.h apparently must be included before X headers though.
- Make sure we use the Imlib2.h here and not the one in /usr/include
Also ensure that the tests build when building without X.
Kim Woelders