Replace tabs with spaces

doc/doxyfile.in

@@ -835,7 +835,7 @@ INPUT_ENCODING         = UTF-8
 # *.f, *.for, *.tcl, *.vhd, *.vhdl, *.ucf and *.qsf.
 
 FILE_PATTERNS          = *.h \
-						 *.hpp
+                         *.hpp
 
 # The RECURSIVE tag can be used to specify whether or not subdirectories should
 # be searched for input files as well.