code review from Josh and Robert

@@ -68,11 +68,11 @@
 .Pp
 .Fn vmem_create
 and
 .Fn vmem_destroy
 create and destroy vmem arenas.  In order to differentiate between arenas used
-for adresses and arenas used for identifiers, the
+for addresses and arenas used for identifiers, the
 .Dv VMC_IDENTIFIER
 flag is passed to
 .Fn vmem_create .
 This prevents identifier exhaustion from being diagnosed as general memory
 failure.

@@ -81,11 +81,11 @@
 .Em spans ,
 or contiguous ranges of integers.  For example, the kernel heap consists of
 just one span:
 .Li "[kernelheap, ekernelheap)" .
 Spans can be added to an arena in two ways: explicitly, by
-.Fn vmem_add ,
+.Fn vmem_add ;
 or implicitly, by importing, as described in
 .Sx Imported Memory
 below.
 .Ss Segments
 Spans are subdivided into

@@ -120,15 +120,16 @@
 requests) is just a subset of
 .Sy heap_arena
 (the kernel heap) that provides caching for the most common slab sizes.  When
 .Sy kmem_va_arena
 runs out of virtual memory, it
-.Em imports more from the heap; we
-say that
+.Em imports
+more from the heap; we say that
 .Sy heap_arena
 is the
-.Em "vmem source" for
+.Em "vmem source"
+for
 .Sy kmem_va_arena.
 .Fn vmem_create
 allows you to specify any existing vmem arena as the source for your new
 arena.  Topologically, since every arena is a child of at most one source, the
 set of all arenas forms a collection of trees.