[Voralphion]

I don't think that trolls could have been made from dwarves, mainly because of their large size difference, but trolls may have been made by Melkor using a similar process and starting material to that which Aule used to make the dwarves. This is of course countered by the Silmarillion, where Eru says to Aule that "... moving when thou thinkest to move them, and if thy thought be elsewhere, standing idle. ..." (Of Aule and Yavanna). From this it says that if Melkor did create them himself, unless his mind was on them, they couldn't move. I believe that he may have got around this by allowing some of his power to disperse into them. This would have the effect of him having his mind on them without him doing so, and allowing them to act independently, and remain after he was throw into the void. This could also explain why they turn to stone in the sun. The sun, being made by the valar from the fruit of one of the trees, would have power to break what ever power Melkor put into the troll, causing them to turn to stone.
In the third age, the addition of Sauron's will and power on some of the trolls may have allowed them to be sun-resistant, hence the Olog-Hai. " Unlike the race of the twilight they could endure the Sun, so long as the will of Sauron held sway over them." (Of Other races, trolls, Appendix F, LOTR).