add the libquadmath-0.dll library file

Author: jniemann66

x64/minGW-W64/QuadMath-readme.txt

@@ -5,5 +5,9 @@ Experimental Quadruple-precision version of ReSampler
 
 * uses Quadruple-Precision (128-bit floating-point) for calculations
 * very slow, because CPU doesn't have 128-bit floating point, so it's implemented in software
-* uses the GNU quad-precision math library
-* Currently no method of reading quad-precision input files. (The best you can do is 64f)
+* uses the GNU quad-precision math library - requires libquadmath-0.dll
+* Currently no method of reading quad-precision input files. (The best you can do is 64f)
+
+Additional Dependencies
+=======================
+libquadmath-0.dll