fix tecs.cpp: use UINT64_C for uint64_t constant instead of UUL

src/lib/mathlib/math/Limits.hpp

@@ -42,6 +42,14 @@
 #include <platforms/px4_defines.h>
 #include <stdint.h>
 
+//this should be defined in stdint.h, but seems to be missing in the ARM toolchain (5.2.0)
+#ifndef UINT64_C
+# if __WORDSIZE == 64
+#  define UINT64_C(c)	c ## UL
+# else
+#  define UINT64_C(c)	c ## ULL
+# endif
+#endif
 namespace math
 {