grep: add new variant to install as ggrep

sysutils/grep/Portfile

@@ -27,8 +27,12 @@ configure.env   PATH=/usr/bin:$env(PATH)
 depends_lib     port:pcre port:gettext
 
 pre-test {
-	reinplace "s|base64 -d|base64 --decode|g" ${worksrcpath}/tests/pcre-jitstack 
+    reinplace "s|base64 -d|base64 --decode|g" ${worksrcpath}/tests/pcre-jitstack
 }
 
 test.run        yes
 test.target     check
+
+variant g_prefix description {Install the program as ggrep} {
+    configure.args-append --program-prefix=g
+}