Another try for M_PI support

Author: ifilot

pyproject.toml

@@ -24,4 +24,4 @@ Homepage = "https://github.com/ifilot/pyqint"
 [tool.cibuildwheel]
 test-requires = "pytest"
 test-command = "pytest {project}/tests"
-skip = ["pp*", "*-win32", "*-manylinux_i686", "cp*-musllinux_*", "cp36-*", "cp37-*", "cp38-*"]
+skip = ["pp*", "*-win32", "*-manylinux_i686", "cp*-musllinux_*", "cp38-*"]

pyqint/integrals.h

@@ -21,6 +21,9 @@
 
 #pragma once
 
+#define _USE_MATH_DEFINES
+#include <cmath>
+
 #include <string>
 #include <unordered_map>
 #include <cstring>