Sort Automake files nicely

The following discussion from !985 (merged) should be addressed:

• @michal started a discussion: (+1 comment)

  I think all such lists should be sorted alphabetically. I mean, why sort *_SOURCES but no AM_CPPFLAGS?

  I can spare you the trouble and do all the sorting myself, and I would leave that for the last moment before merging.

• @michal started a discussion: (+1 comment)

  Apart from block contents, I would also sort the blocks themselves alphabetically, perhaps with LIBLTDL_* being the sole exception. It just seems to make navigating the file a bit easier and - maybe just for me - it indicates that dependency resolution is done elsewhere.

  I think I will stop flagging the sorting issue now and just check everything again later.

• @michal started a discussion: (+1 comment)

  Maybe a matter of taste, but I would first define "standard" library components and then add all the if blocks below that. (Right now, we specify SOURCES, then optional SOURCES, then CFLAGS, then optional CFLAGS; I would change that to SOURCES → CFLAGS → optional SOURCES → optional CFLAGS.)

• @michal started a discussion: (+1 comment)

  Is there any reason for not sorting the entries in each of the AC_CONFIG_FILES blocks above alphabetically? A quick test shows that the order does not matter.

• Ensure Automake if/endif style is consistent tree-wide