New lfun "accent-perispomeni".

This function inserts a COMBINING GREEK PERISPOMENI character that is
normalized to pre-composed characters for base characters where a 
corresponding WITH PERISPOMENI character exists.

This is a partial solution for Ticket #6463.

src/FuncCode.h

@@ -116,6 +116,7 @@ enum FuncCode
 	// 70
 	LFUN_ACCENT_ACUTE,
 	LFUN_ACCENT_TILDE,
+	LFUN_ACCENT_PERISPOMENI,
 	LFUN_ACCENT_CEDILLA,
 	LFUN_ACCENT_MACRON,
 	LFUN_ACCENT_UNDERBAR,

src/LyXAction.cpp

@@ -199,6 +199,14 @@ void LyXAction::init()
  * \endvar
  */
 		{ LFUN_ACCENT_OGONEK, "accent-ogonek", Noop, Edit },
+/*!
+ * \var lyx::FuncCode lyx::LFUN_ACCENT_PERISPOMENI
+ * \li Action: Adds a perispomeni (Greek circumflex)
+               over the next character typed.
+ * \li Syntax: accent-perispomeni
+ * \endvar
+ */
+		{ LFUN_ACCENT_PERISPOMENI, "accent-perispomeni", Noop, Edit },
 /*!
  * \var lyx::FuncCode lyx::LFUN_ACCENT_TIE
  * \li Action: Adds a tie \htmlonly (a͡)\endhtmlonly

src/Text3.cpp

@@ -2268,6 +2268,7 @@ void Text::dispatch(Cursor & cur, FuncRequest & cmd)
 	case LFUN_ACCENT_GRAVE:
 	case LFUN_ACCENT_ACUTE:
 	case LFUN_ACCENT_TILDE:
+	case LFUN_ACCENT_PERISPOMENI:
 	case LFUN_ACCENT_CEDILLA:
 	case LFUN_ACCENT_MACRON:
 	case LFUN_ACCENT_DOT:
@@ -3153,6 +3154,9 @@ bool Text::getStatus(Cursor & cur, FuncRequest const & cmd,
 		break;
 
 	// FIXME: why are accent lfuns forbidden with pass_thru layouts?
+	//  Because they insert COMBINING DIACRITICAL Unicode characters,
+	//  that cannot be handled by LaTeX but must be converted according
+	//  to the definition in lib/unicodesymbols?
 	case LFUN_ACCENT_ACUTE:
 	case LFUN_ACCENT_BREVE:
 	case LFUN_ACCENT_CARON:
@@ -3166,6 +3170,7 @@ bool Text::getStatus(Cursor & cur, FuncRequest const & cmd,
 	case LFUN_ACCENT_OGONEK:
 	case LFUN_ACCENT_TIE:
 	case LFUN_ACCENT_TILDE:
+	case LFUN_ACCENT_PERISPOMENI:
 	case LFUN_ACCENT_UMLAUT:
 	case LFUN_ACCENT_UNDERBAR:
 	case LFUN_ACCENT_UNDERDOT:

src/Trans.cpp

@@ -71,7 +71,9 @@ static TeXAccent lyx_accent_table[] = {
 	{TEX_GRAVE,      0x0300, "grave",           LFUN_ACCENT_GRAVE},
 	{TEX_MACRON,     0x0304, "macron",          LFUN_ACCENT_MACRON},
 	{TEX_TILDE,      0x0303, "tilde",           LFUN_ACCENT_TILDE},
-	{TEX_UNDERBAR,   0x0320, "underbar",        LFUN_ACCENT_UNDERBAR},
+	{TEX_PERISPOMENI, 0x0342, "perispomeni",    LFUN_ACCENT_PERISPOMENI},
+	{TEX_UNDERBAR,   0x0320, "underbar",        LFUN_ACCENT_UNDERBAR}, // COMBINING MINUS SIGN BELOW or 0x0331 COMBINING MACRON BELOW ?
+
 	{TEX_CEDILLA,    0x0327, "cedilla",         LFUN_ACCENT_CEDILLA},
 	{TEX_UNDERDOT,   0x0323, "underdot",        LFUN_ACCENT_UNDERDOT},
 	{TEX_CIRCUMFLEX, 0x0302, "circumflex",      LFUN_ACCENT_CIRCUMFLEX},

src/Trans.h

@@ -42,6 +42,8 @@ enum tex_accent {
 	///
 	TEX_TILDE,
 	///
+	TEX_PERISPOMENI,
+	///
 	TEX_UNDERBAR,
 	///
 	TEX_CEDILLA,