Fix MacOs build

This fixes a list of issues that prevented me from running Licode on Macos (10.9.5). With these changes I can run the Licode basic example successfully with no issues. Hopefully it can help other developers.

- Buffer overflow where generating a random msid was writing the null character outside of the array. The error would show as soon as a single peerconnection is established, it results in crashing the erizo process and a timeout on the client-side.

- Stack overflow due to a large reserved buffer for LOG4CXX formatted strings as defined in the Macro. The error starts to appear when the buffer size exceeds 20,000 characters (it doesn't show for a buffer of 20,000 characters). The crash doesn't occur before a second peer connection is established. It shows in MacOs Console logs as  EXC_BAD_ACCESS and KERN_INVALID_ADDRESS or KERN_PROTECTION_FAILURE.

- Linking error described in https://github.com/ging/licode/issues/157.

- Compiling error showing as [read-only variable is not assignable this->inOutPTMap = offerSdp->inOutPTMap;].