Add zsh ssh colors; update c.vim/template.

Add:
	zsh/prompt.zsh
		-add highlighting to the username and hostname that appear in shells
		controlled by SSH.

	vim/ftplugin/c.vim
		-add highlighting for C global variables (prefixed with a "g_")

	vim/templates/c.txt
		-update main() to return a int indicated the executable's exit status,
		and include stdlib for the EXIT_SUCCESS macro.