Bump version to 5.3.0alpha and soname to 5.3.99.

The idea of 99 is that it looks a bit weird in this context.
For new features there's no API/ABI stability in devel versions.

src/liblzma/Makefile.am

diff --git a/src/liblzma/Makefile.am b/src/liblzma/Makefile.am
index f43280b..6323e26 100644
--- a/src/liblzma/Makefile.am
+++ b/src/liblzma/Makefile.am
@@ -24,7 +24,7 @@
 	-I$(top_srcdir)/src/liblzma/simple \
 	-I$(top_srcdir)/src/common \
 	-DTUKLIB_SYMBOL_PREFIX=lzma_
-liblzma_la_LDFLAGS = -no-undefined -version-info 7:1:2
+liblzma_la_LDFLAGS = -no-undefined -version-info 8:99:3
 
 EXTRA_DIST += liblzma.map validate_map.sh
 if COND_SYMVERS

src/liblzma/api/lzma/version.h

diff --git a/src/liblzma/api/lzma/version.h b/src/liblzma/api/lzma/version.h
index 9682155..2c26ed2 100644
--- a/src/liblzma/api/lzma/version.h
+++ b/src/liblzma/api/lzma/version.h
@@ -21,9 +21,9 @@
  * Version number split into components
  */
 #define LZMA_VERSION_MAJOR 5
-#define LZMA_VERSION_MINOR 2
-#define LZMA_VERSION_PATCH 1
-#define LZMA_VERSION_STABILITY LZMA_VERSION_STABILITY_STABLE
+#define LZMA_VERSION_MINOR 3
+#define LZMA_VERSION_PATCH 0
+#define LZMA_VERSION_STABILITY LZMA_VERSION_STABILITY_ALPHA
 
 #ifndef LZMA_VERSION_COMMIT
 #	define LZMA_VERSION_COMMIT ""