Fix to free(): invalid pointer: #45

[gedeschaines]

Fixes to prevent Policy warnings from syntax errors in CMake code files.

1. File: ./cmake/FindGLEW.cmake

    insert: SET(PROGRAMFILESX86 "PROGRAMFILES(X86)")
    before: SET( GLEW_SEARCH_PATHS
    and
    change: "$ENV{PROGRAMFILES(X86)}/GLEW"   # WINDOWS
        to: "$ENV{${PROGRAMFILESX86}}/GLEW"     # WINDOWS

2. File: ./cmake/FindSDL2.cmake

    insert: SET(PROGRAMFILESX86 "PROGRAMFILES(X86)")
    before: SET( SDL2_SEARCH_PATHS
    and
    change: "$ENV{PROGRAMFILES(X86)}/SDL2"     # WINDOWS
        to: "$ENV{${PROGRAMFILESX86}}/SDL2"   # WINDOWS

3. File: ./cmake/FindASSIMP.cmake

    insert: SET(PROGRAMFILESX86 "PROGRAMFILES(X86)")
    before: SET( ASSIMP_SEARCH_PATHS
    and
    change: "$ENV{PROGRAMFILES(X86)}/ASSIMP"	# WINDOWS
        to: "$ENV{${PROGRAMFILESX86}}/ASSIMP"	# WINDOWS

Fixes to prevent program execution abort on free(): invalid pointer.

1. File: ./src/rendering/texture.h, line 60

    from: void operator=(Texture texture);
      to: Texture& operator=(Texture other) noexcept;

2. File: ./src/rendering/texture.cpp, lines 207-213

   replace:

    void Texture::operator=(Texture texture)
    {
        char* temp[sizeof(Texture)/sizeof(char)];
        memcpy(temp, this, sizeof(Texture));
	memcpy(this, &texture, sizeof(Texture));
        memcpy(&texture, temp, sizeof(Texture));
    }

  with:

    Texture& Texture::operator=(Texture other) noexcept
    {
        //Implemented using move assignment.
    
        //Guard self assignment
        if (this == &other)
            return *this;
    
        if(m_textureData && m_textureData->RemoveReference())
	{
            if(m_fileName.length() > 0)
                s_resourceMap.erase(m_fileName);
	    
	        delete m_textureData;
	}
	m_fileName = other.m_fileName;
        m_textureData = other.m_textureData;
        m_textureData->AddReference();
        return *this;
    }

Originally posted by @gedeschaines in #45 (comment)