Thanks to All,

But your solutions do not like me. And I keep trying the option of Fontfeaturefile page in wiki and Adobe feature topic.
 - http://wiki.contextgarden.net/fontfeaturefiles
 - http://wiki.contextgarden.net/TrueType_fonts_in_luaTeX
 - http://www.adobe.com/devnet/opentype/afdko/topic_feature_file_syntax.html

With this I had found 4 good solutions. 
I think that for Catalans, the best is gemkerndot.fea
I attached files for test.



This is a short sample context file with diferent feature files options
# ============== geminated.tex =============
% Check each feature
\definefontfeature[default][default][featurefile=gemligature.fea]
%\definefontfeature[default][default][featurefile=gemkerndot.fea]
%\definefontfeature[default][default][featurefile=gemkernpair.fea]
%\definefontfeature[default][default][featurefile=gemkerntrio.fea]

 
\starttext
 
\section{Geminated l·l}
COL·LEGI
Col·legi 
Col·Legi
CoL·legi

\stoptext
# ========================================




1.- Create a ligature from L·  and l· to special characters
This option substitute my SED command for replace L· and l· to respective special characters.
# ============== gemligature.fea =============
# Script and language coverage
languagesystem DFLT dflt;
languagesystem latn dflt;


# Ligature
feature liga {
	# Create a ligature
	substitute l \u00b7 by \u0140;
	substitute L \u00b7 by \u013F;
} liga;
# ========================================


2.- Change kerning of middle dot.
This option change middle dot kerning in all cases
# ============== gemkerndot.fea =============
# Script and language coverage
languagesystem DFLT dflt;
languagesystem latn dflt;


# Kerning
feature kern {
	# All middle dots
	position \u00b7 <-330 0 -660 0>;
} kern;
# ========================================


3.- Change kerning of pair middle dot and L characters (suffix and prefix)
This option only change middle dot and L kerning in pair cases
# ============== gemkernpair.fea =============
# Script and language coverage
languagesystem DFLT dflt;
languagesystem latn dflt;


# Kerning
feature kern {
	# Middle dot pair arround 'L'
	position l \u00b7 -330;
	position \u00b7 l -330;
	position L \u00b7 -330;
	position \u00b7 L -330;
} kern;
# ========================================


4.- Change kerning only with trio of L·L and l·l
This option only change middle dot kerning with trio L·L. Have a problem with different L uppercases L·l and l·L
# ============== gemkerntrio =============
# Script and language coverage
languagesystem DFLT dflt;
languagesystem latn dflt;


# Kerning
feature kern {
	# Middle dot arround L·L and l·l
	position l \u00b7' <-330 0 -660 0> l;
	position L \u00b7' <-330 0 -660 0> L;
} kern;
# ========================================



19cat