Allow : character in configuration files.

According to bug #10006, it is needed in some DSL credentials.

As : is not a special character in shell code (at least if
{} is not allowed either) we can safely use it.

config/rootfiles/core/56/filelists/files

@@ -8,3 +8,4 @@ srv/web/ipfire/cgi-bin/media.cgi
 usr/local/bin/hddshutdown
 usr/local/bin/makegraphs
 usr/local/bin/openvpnctrl
+usr/local/bin/readhash

src/scripts/readhash

@@ -13,7 +13,7 @@ VARNAME='[A-Za-z_][A-zA-z0-9_]*'
 
 # For the assigned value we only accept a limited number of characters - none
 # of which are shell metachars
-VARCHARS='A-Za-z0-9=/,._@#+-'
+VARCHARS='A-Za-z0-9=/,.:_@#+-'
 VARVAL="[${VARCHARS}]*"
 
 sed -ne "s/\(${VARNAME}\)=\(${VARVAL}\)$/\1=\2/p" $1