* guix/import/cabal.scm (make-cabal-parser): Add name to section.
(is-lib): Add optional name to regular expression.
(lex-rx-res): Support selecting different substring.
(lex-lib): Match 2nd substring from IS-LIB.
(lex-line): Adapt to changes for lex-lib.
(cabal-library): Add name field and export CABAL-LIBRARY-NAME.
(eval): Remove special case for 'library, which is not required any more.
(make-cabal-section): Move special case for LIBRARY.
* tests/hackage.scm (test-read-cabal-library-name): New variable.
("read-cabal test 1"): Adapt testcase to changed internal structure.
("read-cabal test: library name"): New testcase.