Changes since 0.2.1
1. src/Makefile.in: add install doc targets
2. src/grace-module.c: Added a void* cast to avoid a type-punning
   warning.

Changes since 0.2.0

1. autoconf/aclocal.m4 for better cygwin support
2. src/grace-module.c: Avoid NULL dereference in the close callback