Add ENABLE_LAZY_IMPORTS definition to PC/pyconfig.h

Summary: Lazy Imports 3.14 Windows [enablement](https://www.internalfb.com/diff/D86315832) is failing. This may be because the `ENABLE_LAZY_IMPORTS` macro is not defined in `PC/pyconfig.h`. Unlike other `pyconfig.h` files this file is not automatically generated by `configure`.

Reviewed By: czardoz

Differential Revision: D87348393

fbshipit-source-id: e237e3f1d51116f752ca1810d57b101b9918e4bc

Author: Subbarao Garlapati

PC/pyconfig.h

@@ -107,6 +107,9 @@ WIN32 is still required for the locale module.
 #endif
 #endif
 
+/* Define if you want to enable lazy imports */
+#define ENABLE_LAZY_IMPORTS 1
+
 /* Compiler specific defines */
 
 /* ------------------------------------------------------------------------*/