Various changes suggested by cppcheck

- remove unused variables
- reduce the scope where it makes sense
- correct limits (did you know that strcat()'s last parameter does not
  include the \0 that is always added?)
- set some free()'d pointers to NULL

Source/Core/VideoBackends/OGL/StreamBuffer.cpp

@@ -272,6 +272,7 @@ public:
 		glBindBuffer(m_buffertype, 0);
 		glFinish(); // ogl pipeline must be flushed, else this buffer can be in use
 		FreeAlignedMemory(m_pointer);
+		m_pointer = NULL;
 	}
 
 	std::pair<u8*, size_t> Map(size_t size, u32 stride) {

Source/Core/VideoBackends/OGL/TextureCache.cpp

@@ -55,7 +55,7 @@ static u32 s_DepthCbufid;
 static u32 s_Textures[8];
 static u32 s_ActiveTexture;
 
-bool SaveTexture(const std::string filename, u32 textarget, u32 tex, int virtual_width, int virtual_height, unsigned int level)
+bool SaveTexture(const std::string& filename, u32 textarget, u32 tex, int virtual_width, int virtual_height, unsigned int level)
 {
 	if (GLInterface->GetMode() != GLInterfaceMode::MODE_OPENGL)
 		return false;
@@ -121,7 +121,7 @@ void TextureCache::TCacheEntry::Bind(unsigned int stage)
 	}
 }
 
-bool TextureCache::TCacheEntry::Save(const std::string filename, unsigned int level)
+bool TextureCache::TCacheEntry::Save(const std::string& filename, unsigned int level)
 {
 	return SaveTexture(filename, GL_TEXTURE_2D, texture, virtual_width, virtual_height, level);
 }

Source/Core/VideoBackends/OGL/TextureCache.h

@@ -48,7 +48,7 @@ private:
 			const float *colmat) override;
 
 		void Bind(unsigned int stage) override;
-		bool Save(const std::string filename, unsigned int level);
+		bool Save(const std::string& filename, unsigned int level);
 	};
 
 	~TextureCache();
@@ -59,6 +59,6 @@ private:
 	TCacheEntryBase* CreateRenderTargetTexture(unsigned int scaled_tex_w, unsigned int scaled_tex_h) override;
 };
 
-bool SaveTexture(const std::string filename, u32 textarget, u32 tex, int virtual_width, int virtual_height, unsigned int level);
+bool SaveTexture(const std::string& filename, u32 textarget, u32 tex, int virtual_width, int virtual_height, unsigned int level);
 
 }