Standardize spelling of "userspace".

chapter07/kernfs.xml

@@ -14,7 +14,7 @@
     <primary sortas="e-/dev/">/dev/*</primary>
   </indexterm>
 
-    <para>Applications running in user space utilize various file 
+    <para>Applications running in userspace utilize various file 
     systems created by the kernel to communicate 
     with the kernel itself. These file systems are virtual: no disk
     space is used for them. The content of these file systems resides in

chapter08/libcap.xml

@@ -23,7 +23,7 @@
   <sect2 role="package">
     <title/>
 
-    <para>The Libcap package implements the user-space interface to the POSIX
+    <para>The Libcap package implements the userspace interface to the POSIX
     1003.1e capabilities available in Linux kernels. These capabilities
     partition the all-powerful root privilege into a set of distinct
     privileges.</para>

chapter08/pkgmgt.xml

@@ -55,7 +55,7 @@
         <para>If the Linux kernel needs to be upgraded (for example, from
         5.10.17 to 5.10.18 or 5.11.1), nothing else needs to be rebuilt.
         The system will keep working fine thanks to the well-defined interface
-        between the kernel and user space.  Specifically, Linux API headers
+        between the kernel and userspace.  Specifically, Linux API headers
         need not be (and should not be, see the next item) upgraded
         along with the kernel.  You will merely need to reboot your system to use the
         upgraded kernel.</para>

prologue/why.xml

@@ -328,7 +328,7 @@
       <listitem>
         <para>Libcap</para>
 
-        <para>This package implements the user-space interfaces to
+        <para>This package implements the userspace interfaces to
         the POSIX 1003.1e capabilities available in Linux kernels.
         </para>
       </listitem>