Change lib8tion library to be usable in user keymaps (qmk#5598)

* Move lib8tion header-defined constant into implementation file, add to build

* Move b_m16_interleave initializtion to lib8tion.c, change build to include lib8tion.c in QUANTUM_LIB_SRC

* Remove left-over whitespace

* Move lib8tion include by RGB_MATRIX_ENABLE code in makefile

* Revert build changes and change lib8tion b_m16_interleave constant to static

lib/lib8tion/trig8.h

@@ -147,7 +147,7 @@ LIB8STATIC int16_t cos16( uint16_t theta)
 #endif
 
 
-const uint8_t b_m16_interleave[] = { 0, 49, 49, 41, 90, 27, 117, 10 };
+static const uint8_t b_m16_interleave[8] = { 0, 49, 49, 41, 90, 27, 117, 10 };
 
 /// Fast 8-bit approximation of sin(x). This approximation never varies more than
 /// 2% from the floating point value you'd get by doing