Inline functions not marked with IMGUI_API because apparently it is illegal for MinGW (fix #349)

ARGH C++.

imgui.h

@@ -1160,7 +1160,7 @@ struct ImDrawData
     int             TotalIdxCount;          // For convenience, sum of all cmd_lists idx_buffer.Size
 
     // Functions
-    IMGUI_API ImDrawData() { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; }
+    ImDrawData() { Valid = false; CmdLists = NULL; CmdListsCount = TotalVtxCount = TotalIdxCount = 0; }
     IMGUI_API void DeIndexAllBuffers();               // For backward compatibility: convert all buffers from indexed to de-indexed, in case you cannot render indexed. Note: this is slow and most likely a waste of resources. Always prefer indexed rendering!
     IMGUI_API void ScaleClipRects(const ImVec2& sc);  // Helper to scale the ClipRect field of each ImDrawCmd. Use if your final output buffer is at a different scale than ImGui expects, or if there is a difference between your window resolution and framebuffer resolution.
 };
@@ -1216,7 +1216,7 @@ struct ImFontAtlas
     // Pitch = Width * BytesPerPixels
     IMGUI_API void              GetTexDataAsAlpha8(unsigned char** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel = NULL);  // 1 byte per-pixel
     IMGUI_API void              GetTexDataAsRGBA32(unsigned char** out_pixels, int* out_width, int* out_height, int* out_bytes_per_pixel = NULL);  // 4 bytes-per-pixel
-    IMGUI_API void              SetTexID(void* id)  { TexID = id; }
+    void                        SetTexID(void* id)  { TexID = id; }
 
     // Helpers to retrieve list of common Unicode ranges (2 value per range, values are inclusive, zero-terminated list)
     // (Those functions could be static but aren't so most users don't have to refer to the ImFontAtlas:: name ever if in their code; just using io.Fonts->)
@@ -1268,18 +1268,18 @@ struct ImFont
     ImVector<Glyph>             Glyphs;
     const Glyph*                FallbackGlyph;      // == FindGlyph(FontFallbackChar)
     float                       FallbackXAdvance;   //
-    ImVector<float>             IndexXAdvance;      // Sparse. Glyphs->XAdvance directly indexable (for CalcTextSize functions which are often bottleneck in large UI)
-    ImVector<int>               IndexLookup;        // Sparse. Index glyphs by Unicode code-point
+    ImVector<float>             IndexXAdvance;      // Sparse. Glyphs->XAdvance directly indexable (more cache-friendly that reading from Glyphs, for CalcTextSize functions which are often bottleneck in large UI)
+    ImVector<int>               IndexLookup;        // Sparse. Index glyphs by Unicode code-point.
 
     // Methods
     IMGUI_API ImFont();
     IMGUI_API ~ImFont();
     IMGUI_API void              Clear();
     IMGUI_API void              BuildLookupTable();
-    IMGUI_API float             GetCharAdvance(unsigned short c) const  { return ((int)c < IndexXAdvance.Size) ? IndexXAdvance[(int)c] : FallbackXAdvance; }
     IMGUI_API const Glyph*      FindGlyph(unsigned short c) const;
     IMGUI_API void              SetFallbackChar(ImWchar c);
-    IMGUI_API bool              IsLoaded() const                        { return ContainerAtlas != NULL; }
+    float                       GetCharAdvance(unsigned short c) const  { return ((int)c < IndexXAdvance.Size) ? IndexXAdvance[(int)c] : FallbackXAdvance; }
+    bool                        IsLoaded() const                        { return ContainerAtlas != NULL; }
 
     // 'max_width' stops rendering after a certain width (could be turned into a 2d size). FLT_MAX to disable.
     // 'wrap_width' enable automatic word-wrapping across multiple lines to fit into given width. 0.0f to disable.