Move `mk_def_file_internal() out of mk_util.py` into

``mk_genfile_common.py`` and adapt ``mk_util.py`` and
``mk_def_file.py`` to use the code at its new location.

Whilst I'm here also reindent ``mk_def_file.py`` and make it
use some of the code in ``mk_genfile_common.py`` to avoid code
duplication.

The purpose of this change is to have Python code common to the Python
and CMake build systems separate from Python code that is only used for
the Python build system.

scripts/mk_genfile_common.py

@@ -124,3 +124,36 @@ def mk_z3consts_py_internal(api_files, output_dir):
         api.close()
     z3consts.close()
     return z3consts_output_path
+
+###############################################################################
+# Functions for generating a "module definition file" for MSVC
+###############################################################################
+
+def mk_def_file_internal(defname, dll_name, export_header_files):
+    """
+      Writes to a module definition file to a file named ``defname``.
+
+      ``dll_name`` is the name of the dll (without the ``.dll`` suffix).
+      ``export_header_file`` is a list of header files to scan for symbols
+      to include in the module definition file.
+    """
+    assert isinstance(export_header_files, list)
+    pat1 = re.compile(".*Z3_API.*")
+    fout = open(defname, 'w')
+    fout.write('LIBRARY "%s"\nEXPORTS\n' % dll_name)
+    num = 1
+    for export_header_file in export_header_files:
+        api = open(export_header_file, 'r')
+        for line in api:
+            m = pat1.match(line)
+            if m:
+                words = re.split('\W+', line)
+                i = 0
+                for w in words:
+                    if w == 'Z3_API':
+                        f = words[i+1]
+                        fout.write('\t%s @%s\n' % (f, num))
+                    i = i + 1
+                num = num + 1
+        api.close()
+    fout.close()