Fix pkg-config Cflags

Previously we needed the cflags to include the original HAVE_ICONV value
so that MdbHandle looked the same to client applications as it did to
the compiled library. Now we use a .in file for the header so that these
definitions are not necessary when the client is compiling.

libmdbsql.pc.in

@@ -12,5 +12,4 @@ Description: libmdb based SQL engine
 Requires: libmdb
 Version: @VERSION@
 Libs: -L${libdir} -lmdbsql
-Cflags:
-
+Cflags: -I${includedir}