Make getpath.c easier to follow.

Include/internal/pycore_pathconfig.h

@@ -8,6 +8,23 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#define LOCATION_UNKNOWN (0)
+#define LOCATION_EXISTS (1<<0)
+#define LOCATION_FORCED (1<<1)      /* trusted to exist */
+#define LOCATION_DEFAULT (1<<2)     /* the default value */
+#define LOCATION_CUSTOM (1<<3)      /* from a file or env var */
+/* build-defined */
+#define LOCATION_PREFIX (1<<10)
+#define LOCATION_EXEC_PREFIX (1<<11)
+/* build-related */
+#define LOCATION_IN_BUILD_DIR (1<<15)
+#define LOCATION_IN_SOURCE_TREE (1<<16)
+/* relative */
+#define LOCATION_WITH_FILE (1<<20)  /* in the tree under dirname(<file>)
+                                       (combined with LOCATION_NEAR_*) */
+#define LOCATION_NEAR_ARGV0 (1<<21) /* based on a parent of argv[0] */
+#define LOCATION_NEAR_LIB (1<<22)   /* based on a parent of DLL/SO file */
+
 typedef struct _PyPathConfig {
     /* Full path to the Python program */
     wchar_t *program_full_path;