Reduce Travis parallelism to 15

©! I, Hugo Landau <hlandau@devever.net>, hereby licence these changes under the
©! licence with SHA256 hash
©! fd80a26fbb3f644af1fa994134446702932968519797227e07a1368dea80f0bc.

.travis/script

@@ -16,13 +16,15 @@ fi
 echo Cross-compiling releases...
 mkdir -p "$GOPATH/releasing/idist" "$GOPATH/releasing/dist"
 
+GOX_PARA=15
+
 # cgo crosscompile
 REPOS="github.com/$TRAVIS_REPO_SLUG/..."
-gox -cgo -osarch 'linux/386 linux/amd64' -output "$GOPATH/releasing/idist/ncdns-$TRAVIS_TAG-{{.OS}}_{{.Arch}}/bin/{{.Dir}}" $REPOS
+gox -parallel=$GOX_PARA -cgo -osarch 'linux/386 linux/amd64' -output "$GOPATH/releasing/idist/ncdns-$TRAVIS_TAG-{{.OS}}_{{.Arch}}/bin/{{.Dir}}" $REPOS
 RESULT1=$?
 
 # non-cgo crosscompile
-gox -osarch 'darwin/386 darwin/amd64 linux/arm linux/arm64 linux/ppc64 linux/ppc64le freebsd/386 freebsd/amd64 freebsd/arm openbsd/386 openbsd/amd64 netbsd/386 netbsd/amd64 netbsd/arm dragonfly/amd64 solaris/amd64 windows/386 windows/amd64' -output "$GOPATH/releasing/idist/ncdns-$TRAVIS_TAG-{{.OS}}_{{.Arch}}/bin/{{.Dir}}" $REPOS
+gox -parallel=$GOX_PARA -osarch 'darwin/386 darwin/amd64 linux/arm linux/arm64 linux/ppc64 linux/ppc64le freebsd/386 freebsd/amd64 freebsd/arm openbsd/386 openbsd/amd64 netbsd/386 netbsd/amd64 netbsd/arm dragonfly/amd64 solaris/amd64 windows/386 windows/amd64' -output "$GOPATH/releasing/idist/ncdns-$TRAVIS_TAG-{{.OS}}_{{.Arch}}/bin/{{.Dir}}" $REPOS
 RESULT2=$?
 
 echo cgo crosscompile exited with code $RESULT1