JANITORIAL: Silence some GCC 7 warnings

We have lots and lots of -Wimplicit-fallthrough warnings, and I
don't know if it's worth fixing them or not. But if we want to,
this is how it can be done.

3 files changed, 4 insertions, 3 deletions

diff --git a/engines/agi/global.cpp b/engines/agi/global.cpp
index bd7e4e490f..c44f9e655a 100644
--- a/engines/agi/global.cpp
+++ b/engines/agi/global.cpp
@@ -69,7 +69,7 @@ byte AgiEngine::getVar(int16 varNr) {
 	switch (varNr) {
 	case VM_VAR_SECONDS:
 		getVarSecondsHeuristicTrigger();
-		// is supposed to fall through
+		// fall through
 	case VM_VAR_MINUTES:
 	case VM_VAR_HOURS:
 	case VM_VAR_DAYS:
diff --git a/engines/agi/graphics.cpp b/engines/agi/graphics.cpp
index 3b1b99f458..fa1f11cce4 100644
--- a/engines/agi/graphics.cpp
+++ b/engines/agi/graphics.cpp
@@ -1003,7 +1003,7 @@ void GfxMgr::drawBox(int16 x, int16 y, int16 width, int16 height, byte backgroun
 	case Common::kRenderHercA:
 	case Common::kRenderHercG:
 		lineColor = 0; // change linecolor to black
-		// supposed to fall through
+		// fall through
 	case Common::kRenderCGA:
 	case Common::kRenderEGA:
 	case Common::kRenderVGA:
@@ -1027,7 +1027,7 @@ void GfxMgr::drawDisplayRect(int16 x, int16 y, int16 width, int16 height, byte c
 	case Common::kRenderHercA:
 		if (color)
 			color = 1; // change any color except black to green/amber
-		// supposed to fall through
+		// fall through
 	case Common::kRenderEGA:
 	default:
 		drawDisplayRectEGA(x, y, width, height, color);
diff --git a/engines/sci/engine/kstring.cpp b/engines/sci/engine/kstring.cpp
index 4c5f1228de..3c6a0424f8 100644
--- a/engines/sci/engine/kstring.cpp
+++ b/engines/sci/engine/kstring.cpp
@@ -374,6 +374,7 @@ reg_t kFormat(EngineState *s, int argc, reg_t *argv) {
 			case 'x':
 			case 'u':
 				unsignedVar = true;
+				/* fall through */
 			case 'd': { /* Copy decimal */
 				/* int templen; -- unused atm */
 				const char *format_string = "%d";