build: set the shared library version to 1.0.0

This marks the start of DSO versioning for libwallycore.so.

src/Makefile.am

@@ -197,7 +197,7 @@ libwallycore_la_INCLUDES = \
     include/wally_transaction_members.h
 
 if SHARED_BUILD_ENABLED
-LT_VER_CURRENT = 0   # increment at every ABI change (whether breaking or non-breaking)
+LT_VER_CURRENT = 1   # increment at every ABI change (whether breaking or non-breaking)
 LT_VER_REVISION = 0  # increment at every release, but reset to 0 at every ABI change
 LT_VER_AGE = 0       # increment at every ABI change, but reset to 0 if breaking
 # The library filename will be "libwallycore.so.$((current-age)).$((age)).$((revision))",