Add support of csh (used on FreeBSD)

Signed-off-by: Slava Zanko <slavazanko@gmail.com>

src/subshell.c

@@ -403,6 +403,8 @@ init_subshell (void)
 	    subshell_type = ZSH;
 	else if (strstr (shell, "/tcsh"))
 	    subshell_type = TCSH;
+	else if (strstr (shell, "/csh"))
+	    subshell_type = TCSH;
 	else if (strstr (shell, "/bash") || getenv ("BASH"))
 	    subshell_type = BASH;
 	else if (strstr (shell, "/fish"))