Set core.ignorecase globally

Hi,

Currently, core.ignorecase is set to true on case insensitive system like Windows or Mac on `git init` and `git clone`, and this setting is local to the created/cloned repository.
Here is the man entry:

core.ignorecase
           If true, this option enables various workarounds to enable git to work better on filesystems that are
           not case sensitive, like FAT. For example, if a directory listing finds "makefile" when git expects
           "Makefile", git will assume it is really the same file, and continue to remember it as "Makefile".

           The default is false, except git-clone(1) or git-init(1) will probe and set core.ignorecase true if
           appropriate when the repository is created.

I suggest to set this globally by default when Git is installed, because there is little sense to have this option false on case insensitive systems (it will lead to confusions when renaming a file by changing only the case of letters). 

----------------------------------
Kirill Likhodedov
JetBrains, Inc
http://www.jetbrains.com
"Develop with pleasure!"