Trim trailing whitespaces in build files

Some editors utilizing .editorconfig automatically trim whitespaces. For
convenience this patch removes whitespaces in certain build files:
- ext/*/config*.m4
- configure.ac
- acinclude.m4

Author: petk

config.m4

@@ -46,7 +46,7 @@ if test "$PHP_INTERBASE" != "no"; then
     ], [
       -L$IBASE_LIBDIR
     ])
-  
+
     PHP_ADD_LIBRARY_WITH_PATH($IBASE_LIBNAME, $IBASE_LIBDIR, INTERBASE_SHARED_LIBADD)
     PHP_ADD_INCLUDE($IBASE_INCDIR)
   fi