Fixed texture-mapping for non-ARB textures

When using non-ARB textures, this function:

void ofTexture::allocate(int w, int h, int internalGlDataType, bool bUseARBExtention);

the texture coordinates tex_t and tex_u are not set properly. As the texture size is set to the next power of 2, the texture coordinates are simply set to 1.0, which will produce strange looking results if the texture is not used for sizes matching power of 2.

This bug is not present in:

void ofTexture::allocate(const ofTextureData & textureData);