man.rst: fix spelling mistakes as reported by lintian and Piotr

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>

man.rst/ifup.8.rst

@@ -105,7 +105,7 @@ OPTIONS
                           print iface dependency in list or dot format
 
     -m, --admin-state, --no-scripts
-                          dont run any addon modules/scripts. Only bring
+                          don't run any addon modules/scripts. Only bring
                           the interface administratively up/down
 
     -u, --use-current-config

man.rst/ifupdown-addons-interfaces.5.rst

@@ -950,9 +950,9 @@ EXAMPLES
 
 
     **bridgevlan**: bridgevlan module configures vlan attributes on a 
-    vlan aware bridge. This module only understands vlan interface nam
-    e with dot notations. eg br0.100. where br0 is the vlan aware brid
-    ge this config is for
+    vlan aware bridge. This module only understands vlan interface name
+    with dot notations. eg br0.100. where br0 is the vlan aware bridge
+    this config is for.
 
 
       **bridge-igmp-querier-src**
@@ -1250,7 +1250,7 @@ EXAMPLES
       **address-purge**
 
         **help**: purge existing addresses. By default any existing ip
-        addresses on an interface are purged to match persistant addre
+        addresses on an interface are purged to match persistent addre
         sses in the interfaces file. Set this attribute to 'no'if you 
         want to preserve existing addresses
 

man.rst/interfaces.5.rst

@@ -112,7 +112,7 @@ BUILTIN INTERFACES
     **iface** sections for some interfaces like physical interfaces or vlan
     interfaces in dot notation (like eth1.100) are understood by ifupdown.
     These interfaces do not need an entry in the interfaces file if
-    they are dependents of other interfaces and dont need any specific
+    they are dependents of other interfaces and don't need any specific
     configurations like addresses etc.
 
 EXAMPLES