Adjust MSVC build scripts to parse Makefiles for defines

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