[PATCH] There are several undocumented dependencies

There are several undocumented dependencies in the .spec and in the
INSTALL files. The following is from Fedora, perhaps other RPM
distributions call the packages differently.

Also, the manpages aren't always installed gzipped.

Updates to git-core.spec.in file:
 - Some git scripts use Perl
 - gitk needs wish, which is part of TCL/Tk.
 - curl is used all over
 - Need the ssh program from openssh-clients

Updates to INSTALL:
 - Mention wish
 - Mention ssh

Signed-off-by: Horst H. von Brand <vonbrand@inf.utfsm.cl>