make it possible to build dfuzzer with meson

inspired by https://github.com/matusmarhefka/dfuzzer/pull/24#issuecomment-1107522921

With this patch applied dfuzzer can be built with clang with
```
CC=clang meson build
ninja -C ./build -v
```

meson.build

@@ -0,0 +1,23 @@
+project('dfuzzer', 'c',
+        version : '1.4',
+        default_options: [
+                'c_std=gnu11',
+                'prefix=/usr',
+                'warning_level=2',
+        ],
+)
+
+libgio = dependency('gio-2.0', required : true)
+libffi = dependency('libffi', required : true)
+
+subdir('src')
+
+executable(
+        'dfuzzer',
+        dfuzzer_sources,
+        dependencies : [libgio, libffi],
+        install : true
+)
+
+install_data('src/dfuzzer.conf', install_dir : get_option('sysconfdir'))
+install_man('man/dfuzzer.1')

src/meson.build

@@ -0,0 +1,10 @@
+dfuzzer_sources = files(
+        'dfuzzer.c',
+        'dfuzzer.h',
+        'introspection.c',
+        'introspection.h',
+        'fuzz.c',
+        'fuzz.h',
+        'rand.c',
+        'rand.h',
+)