Unexpected feature

[Gert Jan van Loo]

I try to generate a Verilog include file list using:

INC_DIRS = +incdir+\
/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/memc/+\
/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/common/+\
/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/core/+\
/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/debug/

I find this failing because 'make' does not honour the backslash code at
the end of the line
as any other program: It adds a space!
So the result is:
+incdir+
/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/memc/+
/projec... etc.
This is NOT accepted by the tool. It needs:
+incdir+/projects/maui_vc3/work/gvl/design_database_vc3/verilog_src/memc
/+/projec...

I have several problems with this:
1/ Adding the space is NOT the normal convention used for the backslash
in other programs.
2/ If I want to have a space I can just add it before the backslash. So
there is a 
   simple solution to anybody who wants a space. This in contrast to the
current state where
   I now have to contort myself to remove the spaces again.
   (Which I still have not found how to do, Probably some complex
replace expression)
3/ I have tried to search the info-text but not found this listed
anywhere.
   In fact the \ at the end of the line is used in examples, shortly
commented upon and
   further ignored as something which is 'self-evident'. 

I assume this 'feature' will not be removed as it will break the
makefile of
all simple souls who are not competent enough to add a space in the
right place.

I DO suggest to add this to the manual somewhere and explain in more
details the processing
which takes place when a backslash is at the end of a line:
It adds one space if it is missing and it reduces multiple spaces and
tabs to a single space.
I also suggest you specify how to get rid of these nasty spaces in case
anybody does not want them.

p.s.
Is this a relic from the original 'make'?
I don't have access to an old Unix machine or Make manual so I can't
check this.