extend the intermediate folder with libname_prefix+lib_modifier

[thomas65g]

old: object for debug and release are mixed, because they have the same name
[project_top]\output\vc9_int\VC9_agg\x86
-agg_arc.obj
-agg_arrowhead.obj

new: strictly separated
[project_top]\output\vc9_int\VC9_agg_s\x86
-agg_arc.obj
-agg_arrowhead.obj
...

[project_top]\output\vc9_int\VC9_agg_sd\x86
-agg_arc.obj
-agg_arrowhead.obj
...

[jwillemsen]

When there is no libname_prefix and no use_lib_modifier it looks there is an underscore added to the end, shouldn't that only be added when there is libname_prefix used and add another underscore to the lib_modifier part so that when we have a prefix of foo and a lib_modifier of s we get _foo_s, with only a lib_modifier of foo we get _foo

[thomas65g]

The scope for my request is just to separate the different intermediate files. <%libname_prefix%> was never used on our side in this context – don't know the reason and I just removed it.
<%lib_modifier%> is the key of my request

Without lib_modifier we get foo_ and maybe that looks strange. Also if I move the underscore into the scope of use_lib_modifier it looks strange for intermediate files generated for shared libs in release mode.
The underscore I put in is just for faster reading – a cosmetic feature

shall I do second pull request?

[jwillemsen]

output_subdir is documented as below, I think your changes do change this, or not?
output_subdir = This is used in determining the sub-directory under which intermediate files will be placed.

[thomas65g]

Maybe a change to more general:
output_subdir = This is used in determining the sub-directory under which files will be placed.

In original behavior, executable file and lib files were overwritten by files of other platforms. By reusing the parameter output_subdir I can avoid the behavior
The original folder structure below
├───vc9
├───vc9_int
│ ├───VC9_calc_d
│ │ ├───AMD64
│ │ ├───I386
│ │ └───toradex_ce700
│ └───VC9_main_d
│ ├───AMD64
│ ├───I386
│ └───toradex_ce700
└───vc9_lib

[mitza-oci]

If this PR seeks to change the way output_subdir is used, it should also change the uses in vc7 and vc10 (unless they are already behaving that way).

If I'm reading the *.mpt files right, output_dir is always set to something (unless the user customizes it). I would not be in favor of the defaults output locations of the final binaries (*.dll, *.exe, *.lib) being modified. The default behavior should match what VS itself does when create a simple project using the UI. Other layouts are fine to support as well, but shouldn't be the default.

[thomas65g]

vc10 should be changed to the same way, it's not done; it makes sense. vc7 has no platform support, has it?

I can follow the arguments to have output_dir the exact same way as VS proposed, but how can we avoid that different compilers overwrite target files?

Should vc8platforms.mpt provide an additional template like target_subdir?

target_subdir = This is used in determining the sub-directory under which target files will be placed.

[jwillemsen]

I am concerned that adding the lib_modifier to the output_dir will break user scripts that expect the output in that directory without lib_modifier