Fix GCC7 warnings.

Taken from upstream:
https://git.savannah.gnu.org/cgit/aspell.git/commit/?id=8089fa02122fed0a6394eba14bbedcb1d18e2384

diff --git a/modules/filter/tex.cpp b/modules/filter/tex.cpp
index a979539..19ab63c 100644
--- a/modules/filter/tex.cpp
+++ b/modules/filter/tex.cpp
@@ -174,7 +174,7 @@ namespace {
 
     if (c == '{') {
 
-      if (top.in_what == Parm || top.in_what == Opt || top.do_check == '\0')
+      if (top.in_what == Parm || top.in_what == Opt || *top.do_check == '\0')
 	push_command(Parm);
 
       top.in_what = Parm;
diff --git a/prog/check_funs.cpp b/prog/check_funs.cpp
index db54f3d..89ee09d 100644
--- a/prog/check_funs.cpp
+++ b/prog/check_funs.cpp
@@ -647,7 +647,7 @@ static void print_truncate(FILE * out, const char * word, int width) {
     }
   }
   if (i == width-1) {
-    if (word == '\0')
+    if (*word == '\0')
       put(out,' ');
     else if (word[len] == '\0')
       put(out, word, len);
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<tr><td><span title='2019-06-07 09:57:19 +0200'>2019-06-07</span></td><td><a href='/guix/commit/gnu/services/docker.scm?id=08814aec6ae75adcd059c5235c90ad26e5d5607e'>services: Add Singularity.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/packages/linux.scm (singularity)[source](snippet): Change file
name of setuid helpers in libexec/cli/*.exec.
[arguments]: Remove "--disable-suid".
* gnu/services/docker.scm (%singularity-activation): New variable.
(singularity-setuid-programs): New procedure.
(singularity-service-type): New variable.
* gnu/tests/singularity.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add it.
* doc/guix.texi (Miscellaneous Services): Document it.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-05-05 20:14:15 -0400'>2019-05-05</span></td><td><a href='/guix/commit/gnu/services/docker.scm?id=7a31d93a61e96e631d852a48ddf475704b6a9b04'>services: docker: Add new fields to support proxy.</a><span class='msg-avail'>...<span class='msg-tooltip'>The Docker proxy enables inter-container and outside-to-container loopback,
and is required by the Docker registry server.

* gnu/services/docker.scm (docker-configuration)[proxy,
enable-proxy?]: Add fields.
(docker-shepherd-service): Use them.
(serialize-boolean): New function.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2019-02-11 18:29:01 +0100'>2019-02-11</span></td><td><a href='/guix/commit/gnu/services/docker.scm?id=1c84e68bde61cd5349c38e32d2de0955e141fbce'>services: docker: Make shepherd service also require "dbus-system",</a><span class='msg-avail'>...<span class='msg-tooltip'>"elogind" and "udev".

Fixes &lt;https://bugs.gnu.org/34333&gt;.

* gnu/services/docker.scm (docker-shepherd-service): Require "dbus-system",
"elogind" and "udev".
</span></span></td><td>Danny Milosavljevic</td></tr>
<tr><td><span title='2019-02-11 11:45:12 +0100'>2019-02-11</span></td><td><a href='/guix/commit/gnu/services/docker.scm?id=268e12a89492568f1a8f36bde786ad7f83104bc7'>services: docker: Make shepherd service require "networking".</a><span class='msg-avail'>...<span class='msg-tooltip'>Fixes &lt;https://bugs.gnu.org/34333&gt;.

* gnu/services/docker.scm (docker-shepherd-service): Require "networking".
</span></span></td><td>Danny Milosavljevic</td></tr>