Warnings on imgui on compilation

[Antoine Bolvy]

Currently on dev we have the following warnings displayed:

/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp: In function ‘bool ImFontAtlasBuildWithStbTruetype(ImFontAtlas*)’:
/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:90:38: warning: ‘spc.stbtt_pack_context::nodes’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 #define STBTT_free(x,u)    ((void)(u), ImGui::MemFree(x))
                                      ^
/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:1391:24: note: ‘spc.stbtt_pack_context::nodes’ was declared here
     stbtt_pack_context spc;
                        ^~~
In file included from /home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:98:0:
/home/arch/tmp/Lugdunum/thirdparty/imgui/include/stb_truetype.h:3629:25: warning: ‘spc.stbtt_pack_context::padding’ may be used uninitialized in this function [-Wmaybe-uninitialized]
             stbrp_coord pad = (stbrp_coord) spc->padding;
                         ^~~
/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:1391:24: note: ‘spc.stbtt_pack_context::padding’ was declared here
     stbtt_pack_context spc;
                        ^~~
/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:1391:24: warning: ‘spc.stbtt_pack_context::stride_in_bytes’ may be used uninitialized in this function [-Wmaybe-uninitialized]
/home/arch/tmp/Lugdunum/thirdparty/imgui/src/imgui_draw.cpp:1461:25: warning: ‘spc.stbtt_pack_context::pack_info’ may be used uninitialized in this function [-Wmaybe-uninitialized]
         stbrp_pack_rects((stbrp_context*)spc.pack_info, tmp.Rects, n);
         ~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Would be nice to get rid of them somehow, and to invetigate if we can do something about it upstream.

[ebachard]

Maybe : ocornut/imgui#1445 ?