Preliminary fixes to make linux compiling 'just work'

These fixes make ccl 'just work' when compiling on ubuntu 13.10, probably other setups. Changes:

1) A linux compiler (linux-g++) check in ccl.pro that sets appropriate flags
2) #include <string.h> for several files if compiling on linux
3) 'make clean' removed lexer.cpp and parser.cpp. I think they get autogenerated by make.