Use templates for the package support files

This makes them more easy to reuse in other projects.

build-scripts/release-info.json

@@ -45,7 +45,7 @@
     },
     "files": {
       "": [
-        "build-scripts/pkg-support/mingw/INSTALL.md",
+        "build-scripts/pkg-support/mingw/INSTALL.md.in:INSTALL.md",
         "build-scripts/pkg-support/mingw/Makefile",
         "LICENSE.txt",
         "README.md"
@@ -117,7 +117,7 @@
     },
     "files-devel": {
       "": [
-        "build-scripts/pkg-support/msvc/INSTALL.md",
+        "build-scripts/pkg-support/msvc/INSTALL.md.in:INSTALL.md",
         "LICENSE.txt",
         "README.md"
       ],