Makefile: describe CHARSET_LIB better

The original explanation was not even grammatically correct or
readable.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -59,9 +59,9 @@ all::
 # FreeBSD can use either, but MinGW and some others need to use
 # libcharset.h's locale_charset() instead.
 #
-# Define CHARSET_LIB to you need to link with library other than -liconv to
+# Define CHARSET_LIB to the library you need to link with in order to
 # use locale_charset() function.  On some platforms this needs to set to
-# -lcharset
+# -lcharset, on others to -liconv .
 #
 # Define LIBC_CONTAINS_LIBINTL if your gettext implementation doesn't
 # need -lintl when linking.