[librsvg] rsvg_lt_version_info: set this directly, not with mysterious computations

[Federico Mena Quintero <federico src gnome org>]

commit aac9355fc5fea3a7b3b4c8ff90b045500113d02c
Author: Federico Mena Quintero <federico gnome org>
Date:   Fri Dec 28 13:40:32 2018 -0600

    rsvg_lt_version_info: set this directly, not with mysterious computations
    
    The current values are identical to what was computed before.

 configure.ac | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 92c55808..197f30f5 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,12 +1,27 @@
+# Package version, the "human readable" version
 m4_define([rsvg_major_version],[2])
 m4_define([rsvg_minor_version],[45])
 m4_define([rsvg_micro_version],[2])
 m4_define([rsvg_version],[rsvg_major_version.rsvg_minor_version.rsvg_micro_version])
 
-m4_define([rsvg_lt_major_version],[2])
-m4_define([rsvg_lt_minor_version],[45])
-m4_define([rsvg_lt_micro_version],[2])
-m4_define([rsvg_lt_version_info],m4_eval(rsvg_lt_major_version + 
rsvg_lt_minor_version):rsvg_lt_micro_version:rsvg_lt_minor_version)
+# Library version information.  To make a release:
+#
+# - rsvg_lt_revision += 1
+#
+# - Added interfaces?
+#     rsvg_lt_current += 1
+#     rsvg_lt_revision = 0
+#     rsvg_lt_age += 1
+#
+# - Removed/changed interfaces?
+#     Don't do that! (except for a major release, and only extra-carefully)
+#     rsvg_lt_current += 1
+#     rsvg_lt_revision = 0
+#     rsvg_lt_age = 0
+m4_define([rsvg_lt_current],[47])
+m4_define([rsvg_lt_revision],[2])
+m4_define([rsvg_lt_age],[45])
+m4_define([rsvg_lt_version_info],rsvg_lt_current:rsvg_lt_revision:rsvg_lt_age)
 
 AC_INIT([RSVG],[rsvg_version],[https://gitlab.gnome.org/GNOME/librsvg/issues],[librsvg])