gnu: Sync GNU descriptions with upstream.

From 'guix lint -c gnu-description'.

* gnu/packages/gnunet.scm (gnunet): Adjust description.
* gnu/packages/marst.scm (marst): Likewise.
* gnu/packages/maths.scm (c-graph): Likewise.
* gnu/packages/networking.scm (macchanger): Likewise.

gnu/packages/gnunet.scm

@@ -257,14 +257,12 @@ (define-public gnunet
            %standard-phases)))))
    (synopsis "Secure, decentralized, peer-to-peer networking framework")
    (description
-    "GNUnet is a framework for secure peer-to-peer networking that does not
-use any centralized or otherwise trusted services.  Our high-level goal is to
-provide a strong free software foundation for a global network that provides
-security and privacy.  GNUnet started with an idea for anonymous
-censorship-resistant file-sharing, but has grown to incorporate other
-applications as well as many generic building blocks for secure networking
-applications.  In particular, GNUnet now includes the GNU Name System, a
-privacy-preserving, decentralized public key infrastructure.")
+     "GNUnet is a framework for secure peer-to-peer networking.  The
+high-level goal is to provide a strong foundation of free software for a
+global, distributed network that provides security and privacy.  GNUnet in
+that sense aims to replace the current internet protocol stack.  Along with
+an application for secure publication of files, it has grown to include all
+kinds of basic applications for the foundation of a GNU internet.")
    (license license:gpl3+)
    (home-page "https://gnunet.org/")))
 

gnu/packages/marst.scm

@@ -37,7 +37,10 @@ (define-public marst
         (base32 "0l6swjy8fjrqw89ghc1vvakg21jmpfkpsw92yssrzkg3rg8vkrry"))))
     (build-system gnu-build-system)
     (home-page "http://www.gnu.org/software/marst")
-    (synopsis "Algol to C translator")
-    (description "MARST is an Algol-to-C translator.  It automatically translates programs
-written on the algorithmic language Algol 60 to the C programming language.")
+    (synopsis "Algol-to-C translator")
+    (description
+     "GNU MARST is an Algol-to-C translator.  The package consists of the
+translator itself, a library that contains the necessary Algol 60 procedures,
+and a converter that converts existing Algol 60 programs from other
+representations to the MARST representation.")
     (license gpl3+)))

gnu/packages/maths.scm

@@ -102,10 +102,13 @@ (define-public c-graph
    (build-system gnu-build-system)
    (inputs
      `(("fortran" ,gfortran)))
-   (synopsis "Visualize and analyze convolution operations")
+   (synopsis "Visualizing and demonstrating convolution")
    (description
-    "GNU C-Graph demonstrates the theory of convolution underlying
-engineering systems and signal analysis.")
+     "GNU C-Graph is a tool for demonstrating the theory of convolution.
+Thus, it can serve as an excellent aid to students of signal and systems
+theory in visualizing the convolution process.  Rather than forcing the
+student to write code, the program offers an intuitive interface with
+interactive dialogs to guide them.")
    (license license:gpl3+)
    (home-page "http://www.gnu.org/software/c-graph/")))
 

gnu/packages/networking.scm

@@ -62,7 +62,7 @@ (define-public macchanger
                 "1xsiivjjyhqcs6dyjcshrnxlgypvyfzacjz7gcjgl88xiw9lylri"))))
     (build-system gnu-build-system)
     (home-page "http://www.gnu.org/software/macchanger")
-    (synopsis "Display or change the MAC address of networking devices")
+    (synopsis "Viewing and manipulating MAC addresses of network interfaces")
     (description "GNU MAC Changer is a utility for viewing and changing MAC
 addresses of networking devices.  New addresses may be set explicitly or
 randomly.  They can include MAC addresses of the same or other hardware vendors