SDLvncviewer: fix Ctrl+<letter>

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

TODO

@@ -4,7 +4,6 @@ immediate:
 Implement ZYWRLE decoding in libvncclient
 make SDLvncviewer more versatile (test for missing keys, introduce scrollbars,
 	make scrollable with 2xCtrl and mouse drag)
-	- Left Ctrl + A does not work
 	- 2nd and 3rd mouse button are switched
 Clean up ZRLE (probably not thread-safe: zrleBeforeBuf, zrlePaletteHelper)
 style fixes: use Linux' coding guidelines & ANSIfy tightvnc-filetransfer:

client_examples/SDLvncviewer.c

@@ -130,6 +130,11 @@ static rfbKeySym SDL_key2rfbKeySym(SDL_KeyboardEvent* e) {
 	case SDLK_BREAK: k = XK_Break; break;
 	default: break;
 	}
+	if (k == 0 && e->keysym.sym >= SDLK_a && e->keysym.sym <= SDLK_z) {
+		k = XK_a + e->keysym.sym - SDLK_a;
+		if (e->keysym.mod & (KMOD_LSHIFT | KMOD_RSHIFT))
+			k &= ~0x20;
+	}
 	if (k == 0) {
 		if (e->keysym.unicode < 0x100)
 			k = e->keysym.unicode;