Prepare initial release

There are plenty of unreleased variants of libsecp256k1 version 0.1.0
(libsecp256k1.so.0.0.0) in the wild. We choose a new version number to allow a
clear distinction.

There are variants of 0.1.0 that are incompatible with the initial release,
hence we increase the minor version to arrive at version number 0.2.0. For the
same reason, we increase the LIB_VERSION_CURRENT and keep AGE at 0.

CHANGELOG.md

@@ -1,11 +1,21 @@
 # Changelog
 
-This file is currently only a template for future use.
-
-Each change falls into one of the following categories: Added, Changed, Deprecated, Removed, Fixed or Security.
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+## [0.2.0] - YYYY-MM-DD
+
+- Initial release
+
+## [0.1.0] - 2013-03-05 to YYYY-MM-DD
+
+This version was never actually released.
+The number was given by the build system since the introduction of autotools in Jan 2014 (ea0fe5a5bf0c04f9cc955b2966b614f5f378c6f6).
+Therefore, this version number does not uniquely identify a set of source files.
+
+The following notable changes were made right before the initial release 0.2.0:
+
 ### Changed
  - Enable modules schnorrsig, extrakeys and ECDH by default in ./configure
 
@@ -15,8 +25,3 @@ Each change falls into one of the following categories: Added, Changed, Deprecat
 
 ### Added
  - Added `secp256k1_selftest`, to be used in conjunction with `secp256k1_context_static`.
-
-## [MAJOR.MINOR.PATCH] - YYYY-MM-DD
-
-### Added/Changed/Deprecated/Removed/Fixed/Security
-- [Title with link to Pull Request](https://link-to-pr)

configure.ac

@@ -4,7 +4,7 @@ AC_PREREQ([2.60])
 # the API. All changes in experimental modules are treated as
 # backwards-compatible and therefore at most increase the minor version.
 define(_PKG_VERSION_MAJOR, 0)
-define(_PKG_VERSION_MINOR, 1)
+define(_PKG_VERSION_MINOR, 2)
 define(_PKG_VERSION_BUILD, 0)
 define(_PKG_VERSION_IS_RELEASE, false)
 
@@ -13,7 +13,7 @@ define(_PKG_VERSION_IS_RELEASE, false)
 # https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
 # All changes in experimental modules are treated as if they don't affect the
 # interface and therefore only increase the revision.
-define(_LIB_VERSION_CURRENT, 0)
+define(_LIB_VERSION_CURRENT, 1)
 define(_LIB_VERSION_REVISION, 0)
 define(_LIB_VERSION_AGE, 0)