Rewrite Configure to handle the target values as hash tables.

Rewrite Configure to handle the target values as hash tables.

The reasoning is that configuration strings are hard to read and error
prone, and that a better way would be for them to be key => value hashes.

Configure is made to be able to handle target configuration values as a
string as well as a hash.  It also does the best it can to combine a
"debug-foo" target with a "foo" target, given that they are similar
except for the cflags and lflags values.  The latter are spliced into
options that are common for "debug-foo" and "foo", options that exist
only with "debug-foo" and options that exist only with "foo", and make
them into combinable attributes that holds common cflags, extra cflags
for debuggin and extra cflags for non-debugging configurations.

The next step is to make it possible to have template configurations.

Reviewed-by: Andy Polyakov <appro@openssl.org>