build: introduce shared libreiserfscore.so and export it

In order to use reiserfs functionality in external programs, we need to
make a shared library and includes available.

This converts both libmisc and libreiserfscore into shared libraries, and
links libmisc into libreiserfscore. We also export the includes and
a pkg-config file.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

lib/Makefile.am

@@ -1,5 +1,5 @@
-noinst_LIBRARIES = libmisc.a
+noinst_LTLIBRARIES = libmisc.la
 
-libmisc_a_SOURCES = io.c misc.c parse_time.c progbar.c
+libmisc_la_SOURCES = io.c misc.c parse_time.c progbar.c
 ##reiserfs.c