gnu: Add Test-LongString.

* gnu/packages/perl.scm (perl-test-longstring): New variable.

gnu: Add Catalyst-Action-REST.

* gnu/packages/web.scm (perl-catalyst-action-rest): New variable.

gnu: Add URI-Find.

* gnu/packages/web.scm (perl-uri-find): New variable.

gnu: agg: Add explanatory comment to the patch.

* gnu/packages/patches/agg-am_c_prototype.patch: Add comment.

gnu: libxrandr: Propagate more inputs.

* gnu/packages/xorg.scm (libxrandr): Propagate libxrender, xproto, libx11.

gnu: mesa: Enable more optional features.

* gnu/packages/gl.scm (mesa): Enable DRM support of EGL, thread local storage
  in GLX, and off-screen rendering.

gnu: mesa: Fix file names passed to dlopen(3).

* gnu/packages/gl.scm (mesa): Patch source files to make file names passed to
  dlopen(3) absolute.

gnu: Add perl-svg.

* gnu/packages/perl.scm (perl-svg): New variable.

gnu: Add colordiff.

* gnu/packages/patchutils.scm (colordiff): New variable.

ftp-client: Switch to binary mode before using the "SIZE" command.

* guix/ftp-client.scm (ftp-size): Add '%ftp-command' call.

lint: Report details about FTP errors.

* guix/scripts/lint.scm (probe-uri) <'ftp>: Pass more information about
  failures alongside 'ftp-response.
  (validate-uri) <ftp-response>: Handle it, and adjust "not reachable"
  message accordingly.

lint: Change misleading variable name.

* guix/scripts/lint.scm (probe-uri) <'ftp>: Rename 'port' to 'conn'.

gnu: Add mesa-utils.

* gnu/packages/gl.scm (mesa-utils): New variable.
(mesa-demos-source): New procedure.

gnu: mesa: Propagate inputs libxshmfence and libxfixes.

* gnu/packages/gl.scm (mesa): Propagate inputs libxshmfence and libxfixes.

gnu: mesa: Add input s2tc.

* gnu/packages/gl.scm (mesa): Add input s2tc, patch sources to make the
  reference to libtxc_dxtn.so absolute since it's passed to dlopen(3).

gnu: Add s2tc.

* gnu/packages/gl.scm (s2tc): New variable.
(mesa-headers): New variable.

gnu: msmtp: Use mirror:// URI.

* gnu/packages/mail.scm (msmtp): Use a mirror:// URI for the source.

gnu: claws-mail: Use mirror:// URI.

* gnu/packages/mail.scm (claws-mail): Use a mirror:// URI for the source.

gnu: procps: Explain why a mirror:// URI isn't used.

* gnu/packages/linux.scm (procps): Add a comment explaining why we don't use a
  mirror:// URI.

gnu: lcms: Use mirror:// URI.

* gnu/packages/ghostscript.scm (lcms): Use a mirror:// URI for the source.