gcc complains about (intended) implicit fall-through

Because we compile with "-Werror" each warning is an error. In this
parser an implicit fall-through is used in a switch() statement, which
is typically a bad thing, but not unheard of.

In this code it was checked + verified that it was the intent to fall
through. So the warning was disabled.

CMakeLists.txt

@@ -20,5 +20,8 @@ cmake_policy(SET CMP0014 NEW)
 find_package(BISON)
 find_package(FLEX)
 
+# Make gcc not warn about implicit fall through
+SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-implicit-fallthrough")
+
 # include source directory for library target 'vex'
 add_subdirectory(src)