Fix type comparison issue that is a hard error in GCC 10.

Taken from upstream:

  https://github.com/OpenTTD/grfcodec/commit/bb692b2c723c5e87cc8f89f445928e97594d5b8f

diff --git a/src/command.cpp b/src/command.cpp
index 9aa0e14..1f32cf1 100644
--- a/src/command.cpp
+++ b/src/command.cpp
@@ -300,8 +300,9 @@ bool parse_comment(const string&line){
 		break;
 	case BEAUTIFY:{
 		commandstream>>command_part;
-		uint val=find_command(command_part,beaut),togglebit;
-		if(val!=(uint)-1&&val!=OFF)_commandState.beautifier=true;
+		int val=find_command(command_part,beaut);
+		uint togglebit;
+		if(val!=-1&&val!=OFF)_commandState.beautifier=true;
 		switch(val){
 		case -1:
 			IssueMessage(0,COMMAND_INVALID_ARG,gen[BEAUTIFY].name);
@@ -372,7 +373,7 @@ bool parse_comment(const string&line){
 dotoggle:
 			commandstream>>command_part;
 			val=find_command(command_part,beaut);
-			if(!commandstream||val==(uint)-1){
+			if(!commandstream||val==-1){
 				IssueMessage(0,COMMAND_INVALID_ARG,gen[BEAUTIFY].name);
 				return true;
 			}
about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>refs</a><a class='active' href='/guix/log/doc/htmlxref.cnf'>log</a><a href='/guix/tree/doc/htmlxref.cnf?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>tree</a><a href='/guix/commit/doc/htmlxref.cnf?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>commit</a><a href='/guix/diff/doc/htmlxref.cnf?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/doc/htmlxref.cnf'>
<input type='hidden' name='id' value='0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>root</a>/<a href='/guix/log/doc?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>doc</a>/<a href='/guix/log/doc/htmlxref.cnf?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd'>htmlxref.cnf</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/doc/htmlxref.cnf?id=0ee0dfcc4a576ff9536c979d50a4ec2223b3a3fd&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-01-12 00:19:10 +0100'>2020-01-12</span></td><td><a href='/guix/commit/doc/htmlxref.cnf?id=30d83f445b70ebce7f01eaa91c8f418ff0a98321'>doc: Update htmlxref.cnf.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/htmlxref.cnf: Update from Texinfo.  Add entries for "mes",
"guix.ru", and "guix.zh_CN".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-05-04 23:07:38 +0200'>2019-05-04</span></td><td><a href='/guix/commit/doc/htmlxref.cnf?id=e8f8363cdebb24dc359cadba7ae0a689fb21fb99'>doc: Update htmlxref.cnf.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/htmlxref.cnf (G): Switch to https.
(geiser, guix.de, guix.es, hurd): New entries.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-05 22:16:10 +0200'>2018-07-05</span></td><td><a href='/guix/commit/doc/htmlxref.cnf?id=c35f77c5a07690fc9d369ed4b751a5a9e5de6cf1'>doc: Update URL of the Emacs-Guix manual.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/htmlxref.cnf (EMACS_GUIX): Update URL.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-05 22:13:23 +0200'>2018-07-05</span></td><td><a href='/guix/commit/doc/htmlxref.cnf?id=56b4dabc2ba3446ff212e0d4d9e2df15fc25e88f'>doc: Mention translations of the manual.</a><span class='msg-avail'>...<span class='msg-tooltip'>* doc/guix.texi (Top): Add note about l10n.
* doc/htmlxref.cnf: Add "guix.fr".
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-05-30 18:30:39 +0300'>2017-05-30</span></td><td><a href='/guix/commit/doc/htmlxref.cnf?id=f753c2829913a9bb61dc266f4b1db8275e34a461'>doc: htmlxref: Fix link to Emacs-Guix manual.</a><span class='msg-avail'>...<span class='msg-tooltip'>Reported-by: Ludovic Courtès &lt;ludo@gnu.org&gt;

This fixes a regression introduced by commit
8ca0c88a894c685b624757e38ee7663534f03460.

* doc/htmlxref.cnf (EMACS_GUIX): Fix the link to 'html_node'.
</span></span></td><td>Alex Kost</td></tr>