#8 Improve const-correctness

[Markus Elfring]

Would you like to apply the advices from the article "http://en.wikipedia.org/wiki/Const-correctness" to more places in your sources?
I suggest to add the key word "const" to the type specifiers for parameters like the following.
- http://gull.svn.sourceforge.net/viewvc/gull/seagull/trunk/src/generator-stats/C_GeneratorStats.hpp?revision=101&view=markup
name, extension (function "setFileName")
P_listeStr (function "isWellFormed")

- http://gull.svn.sourceforge.net/viewvc/gull/seagull/trunk/src/protocol-data/ProtocolData.hpp?revision=156&view=markup
P_Source (function "copyValue")