add a .gitignore file to ignore unneeded files from development releases

.gitignore

+# intermediate build output:
+
+*.o
+
+# libraries
+
+src/libespeak.a
+src/libespeak.so*
+
+# programs:
+
+platforms/*/espeak-phoneme-data
+src/espeak
+src/espeakedit
+src/speak
+
+# espeak-data
+
+dictsource/en_extra
+
+espeak-data/dictsource
+espeak-data/phsource
+espeak-data/*_dict
+espeak-data/intonations
+espeak-data/phondata
+espeak-data/phondata-manifest
+espeak-data/phonindex
+espeak-data/phontab
+
+# other (from espeak development releases)
+
+espeak-data/config
+phsource/compile_prog_log