doc: make -f Makefile.doc (#2919)

mechanical change: create the manual pages.

Signed-off-by: Miek Gieben <miek@miek.nl>

man/coredns-metrics.7

@@ -1,12 +1,12 @@
 .\" Generated by Mmark Markdown Processer - mmark.nl
-.TH "COREDNS-METRICS" "7" "April 2019" "CoreDNS" "CoreDNS Plugins"
+.TH "COREDNS-METRICS" 7 "June 2019" "CoreDNS" "CoreDNS Plugins"
 
-.SH NAME
+.SH "NAME"
 .PP
 \fIprometheus\fP - enables Prometheus
 \[la]https://prometheus.io/\[ra] metrics.
 
-.SH DESCRIPTION
+.SH "DESCRIPTION"
 .PP
 With \fIprometheus\fP you export metrics from CoreDNS and any plugin that has them.
 The default location for the metrics is \fB\fClocalhost:9153\fR. The metrics path is fixed to \fB\fC/metrics\fR.
@@ -63,7 +63,7 @@ name "dropped" (without a closing dot - this is never a valid domain name).
 .PP
 This plugin can only be used once per Server Block.
 
-.SH SYNTAX
+.SH "SYNTAX"
 .PP
 .RS
 
@@ -80,7 +80,7 @@ For each zone that you want to see metrics for.
 It optionally takes a bind address to which the metrics are exported; the default
 listens on \fB\fClocalhost:9153\fR. The metrics path is fixed to \fB\fC/metrics\fR.
 
-.SH EXAMPLES
+.SH "EXAMPLES"
 .PP
 Use an alternative listening address:
 
@@ -110,7 +110,7 @@ then:
 .fi
 .RE
 
-.SH BUGS
+.SH "BUGS"
 .PP
 When reloading, the Prometheus handler is stopped before the new server instance is started.
 If that new server fails to start, then the initial server instance is still available and DNS queries still served,