autotools: autotools'ify libsecp256k1

.gitignore

@@ -1,7 +1,34 @@
-obj/*
 bench
+bench.exe
 tests
+tests.exe
 *.so
 *.a
-config.mk
 !.gitignore
+
+Makefile
+configure
+.libs/
+Makefile.in
+aclocal.m4
+autogen.sh
+autom4te.cache/
+config.log
+config.status
+*.tar.gz
+*.la
+libtool
+.deps/
+.dirstamp
+src/build-aux/
+*.lo
+*.o
+*~
+src/libsecp256k1-config.h
+src/libsecp256k1-config.h.in
+m4/libtool.m4
+m4/ltoptions.m4
+m4/ltsugar.m4
+m4/ltversion.m4
+m4/lt~obsolete.m4
+src/stamp-h1