gitignore: Restructure existing rules

Organize the rules into groups corresponding to the tools creating
these files.

Use blank lines and comments for clarity.

.gitignore

@@ -1,3 +1,6 @@
+# extension txt
+*.txt
+
 # project files
 .*project
 Project.*
@@ -23,9 +26,22 @@ uninstall.vcproj
 *.vcproj.*.user
 projectfiles/VC[12]*
 
+# eclipse
+.settings
+
+# autotools
+config.h
+config.h.in
+config.log
+config.status
+configure
+configure.lineno
+aclocal.m4
+autom4te.cache
+stamp-h1
+
 # build directories
 /wesnothd*
-/test*
 /wesnoth*
 /campaignd*
 /cutter*
@@ -52,35 +68,26 @@ Lib
 translations
 userdata
 
-# configuration
-config.h
-config.h.in
-config.log
-config.status
-configure
-configure.lineno
+# testing
+/test*
+error*.log
+do_build_and_tests.sh
+boost_test_result.xml
+
+# translations
+locales
+make_translation
+merge_translations
 
 # OS created files
 .DS_Store
-Thumbs.db
+[Tt]humbs.db
+*Neuer Ordner*
 
 # uncategorized
-.settings
-*.txt
 *.swp
-*.gmo
-make_translation
-merge_translations
 Makefile
 Makefile.in
-autom4te.cache
-stamp-h1
 revision.h
-aclocal.m4
 6not
-boost_test_result.xml
-locales
 .kdev*
-*Neuer Ordner*
-error*.log
-do_build_and_tests.sh