Add OpenMP libraries and pragmas.
Add critical section around addition.
We're changing a shared value, so it needs to be accessed separately.
Add p to the shared variable list.
p doesn't change during the loop, so it can be shared without any problem.
Merge branch 'master' of https://github.com/ofb/c

Conflicts:
	char.c++
Merge pull request #3 from geppettodivacin/master

Add OpenMP.