Adjust MSVC build scripts to parse Makefiles for defines

This adjusts the MSVC build scripts to look at the compile flags mentioned
in the Makefile to look for -D arguments in order to determine which
constants should be defined in Visual Studio builds.

One small anomaly that appeared as a result of this change is that the
Makefile for the ltree contrib module defined LOWER_NODE, but this was
not properly defined in the MSVC build scripts.  This meant that MSVC
builds would differ in case sensitivity in the ltree module when
compared to builds using a make build environment.  To maintain the same
behavior here we remove the -DLOWER_NODE from the Makefile and just always
define it in ltree.h for non-MSVC builds.  We need to maintain the old
behavior here as this affects the on-disk compatibility of GiST indexes
when using the ltree type.

The only other resulting change here is that REFINT_VERBOSE is now defined
for the autoinc, insert_username and moddatetime contrib modules.
Previously on MSVC, this was only defined for the refint module.  This
aligns the behavior to build environments using make as all 4 of these
modules share the same Makefile.

Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/CAApHDvpo6g5csCTjc_0C7DMvgFPomVb0Rh-AcW5afd=Ya=LRuw@mail.gmail.com

contrib/ltree/crc32.c

@@ -8,6 +8,7 @@
  */
 
 #include "postgres.h"
+#include "ltree.h"
 
 #ifdef LOWER_NODE
 #include <ctype.h>