Build on modern macOS

Three source patches the modern clang/C++ frontend requires:
- graphics/window.cpp: strchr on const char* now returns const char*
- filemap.cpp, prefs.cpp: C++11 forbids no-space concatenation of a
  string literal with an adjacent macro identifier

Autotools state regenerated with autoreconf -fi against current
autoconf/automake so configure can be run on macOS 26 / Apple Silicon.

Added run-kobodl.sh to launch the binary from the source tree (the
compiled-in data paths assume a .app bundle), and a .gitignore for
build artifacts.

Out-of-tree dependency: SDL_image 1.2 must be built with
--disable-imageio. Apple's ImageIO backend in IMG_ImageIO.m yields
SDL_Surfaces with all-zero pixel data on current macOS, leaving every
sprite invisible; libpng decodes correctly.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,22 @@
+# Build artifacts
+*.o
+*.a
+*.lo
+*.la
+.deps/
+.libs/
+
+# autotools generated state (regenerated by configure)
+Makefile
+!data/gfx/Makefile.am
+!data/sfx/Makefile.am
+autom4te.cache/
+config.log
+config.status
+stamp-h1
+Info.plist
+*~
+
+# Local build outputs
+kobodl
+log.txt