Fix many GCC -Wimplicit-fallthrough warnings (#243)

This commit adds '/* FALLTHROUGH */' comments to fix many
GCC warnings when compiling with -Wimplicit-fallthrough.
Additionally, the existing fallthrough comments have been
changed for consistency.

src/lib/libast/port/astlicense.c

@@ -753,7 +753,7 @@ astlicense(char* p, int size, char* file, char* options, int cc1, int cc2, int c
 							break;
 						case -1:
 							c = SPECIAL;
-							/*FALLTHROUGH*/
+							/* FALLTHROUGH */
 						default:
 							notice.type = c;
 							notice.item[CLASS].data = lic[lic[c].quote].data;

src/lib/libast/port/astquery.c

@@ -89,7 +89,7 @@ astquery(int quit, const char* format, ...)
 		{
 		case EOF:
 			n = c;
-			/*FALLTHROUGH*/
+			/* FALLTHROUGH */
 		case '\n':
 			switch (n)
 			{

src/lib/libast/port/mc.c

@@ -171,7 +171,7 @@ mcfind(const char* locale, const char* catalog, int category, int nls, char* pat
 						p += sizeof(lc_messages) - 1;
 						goto case_C;
 					}
-					/*FALLTHROUGH*/
+					/* FALLTHROUGH */
 				default:
 					if (s < e)
 						*s++ = c;