AP_InternalError: added invalid_arguments failure

this is intended to catch problems where we have unexpectedly received
invalid arguments.  For example an out-of-bounds target speed that
should have been caught somewhere else.

running out of bits so we use a single bit to capture invalid inputs to or output from a calculation

libraries/AP_InternalError/AP_InternalError.cpp

@@ -61,6 +61,7 @@ void AP_InternalError::errors_as_string(uint8_t *buffer, const uint16_t len) con
         "mem_guard",
         "dma_fail",
         "params_restored",
+        "invalid arguments",
     };
 
     static_assert((1U<<(ARRAY_SIZE(error_bit_descriptions))) == uint32_t(AP_InternalError::error_t::__LAST__), "too few descriptions for bits");

libraries/AP_InternalError/AP_InternalError.h

@@ -66,7 +66,8 @@ public:
         mem_guard                   = (1U << 26),  //0x4000000 67108864
         dma_fail                    = (1U << 27),  //0x8000000 134217728
         params_restored             = (1U << 28),  //0x10000000 268435456
-        __LAST__                    = (1U << 29),  // used only for sanity check
+        invalid_arg_or_result       = (1U << 29),  //0x20000000 536870912
+        __LAST__                    = (1U << 30),  // used only for sanity check
     };
 
     // if you've changed __LAST__ to be 32, then you will want to