Fix definitions for the unknown distro/installation

If the distro/installation really is unsupported (i.e. unknown) we should
not make it look like a known distribution (i.e. RHEL) complete with
dependencies on other RPMs and trying to find kenrel source in the RH
standard location.

Additionally add 'k' prefix for kernel requires for consistency.

spl-modules.spec.in

@@ -125,14 +125,11 @@
 
 # Unsupported distro:
  %if %{undefined kver}
-  %define kver           X
+  %define kver           %(uname -r)
  %endif
- %define kpkg            kernel
- %define kdevpkg         kernel-devel
  %define kverpkg         %{kver}
- %define koppkg          =
  %if %{undefined kdir}
-  %define kdir           %{_usrsrc}/kernels/%{kver}
+  %define kdir           /lib/modules/%{kver}/build
  %endif
  %if %{undefined kobj}
   %define kobj           %{kdir}
@@ -159,9 +156,13 @@
 %else
 %define relext           %(echo %{kverpkg} | %{__sed} -e 's/-/_/g')
 %define release          @SPL_META_RELEASE@_%{relext}
-%define requires         %{kpkg} %{koppkg} %{kverpkg}
+%if %{defined kpkg}
+%define krequires        %{kpkg} %{koppkg} %{kverpkg}
+%endif
+%if %{defined kdevpkg}
 %define devel_requires   %{kdevpkg} %{koppkg} %{kverpkg}
 %endif
+%endif
 
 Summary:         Solaris Porting Layer Modules
 Group:           Utilities/System
@@ -172,8 +173,12 @@ License:         @LICENSE@
 URL:             git://eris.llnl.gov/spl.git
 BuildRoot:       %{_tmppath}/%{name}-%{version}-%{release}-%(%{__id} -un)
 Source:          @PACKAGE@-%{version}.tar.gz
-Requires:        %{requires}
+%if %{defined krequires}
+Requires:        %{krequires}
+%endif
+%if %{defined kdevpkg}
 BuildRequires:   %{kdevpkg}
+%endif
 
 %description
 The %{name} package contains kernel modules for emulating Solaris style
@@ -184,8 +189,12 @@ taskq, thread, time, and vnode APIs.
 %package devel
 Summary:         Solaris Porting Layer Headers and Symbols
 Group:           Development/Libraries
+%if %{defined devel_requires}
 Requires:        %{devel_requires}
+%endif
+%if %{defined kdevpkg}
 BuildRequires:   %{kdevpkg}
+%endif
 
 %description devel
 The %{name}-devel package contains the header files and Module{s}.symvers