> Please try the patch below.  It works for me.

Well, I've finally managed to install a working "patch" utility for
Windows (MinGW has a package for it).

I've applied the patch and built the branch.

Now, after starting emacs (-Q -nw) and typing "áéíóúñç", Emacs shows
different symbols (see attached screenshot), but if I copy them and
paste here, the pasted symbols are the correct ones (áéíóúñç), instead
of the ones I see in the screen.

Also, if I go to one char, for example the "á", and do C-u C-x =,
Emacs says (*):

             position: 192 of 196 (97%), column: 0
            character: á (displayed as á) (codepoint 225, #o341, #xe1)
    preferred charset: iso-8859-1 (Latin-1 (ISO/IEC 8859-1))
code point in charset: 0xE1
               syntax: w 	which means: word
             category: .:Base, L:Left-to-right (strong), c:Chinese,
j:Japanese, l:Latin, v:Viet
             to input: type "C-x 8 RET HEX-CODEPOINT" or "C-x 8 RET NAME"
          buffer code: #xC3 #xA1
            file code: #xE1 (encoded by coding system iso-latin-1-dos)
              display: terminal code #xE1

Character code properties: customize what to show
  name: LATIN SMALL LETTER A WITH ACUTE
  old-name: LATIN SMALL LETTER A ACUTE
  general-category: Ll (Letter, Lowercase)
  decomposition: (97 769) ('a' '́')

There are text properties here:
  fontified            t


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(*) Although, as I said, in the second line I don't see the "á"
symbols in the screen, but another symbols (like a greek "beta").

-- 
Dani Moncayo