maint: spec: use pkgconfig for glib-2.0

...as this is the only reference configure script uses.

References:
http://rpm.org/gitweb?p=rpm.git;a=commit;h=6c4b0fc (~2007)

booth.spec

@@ -42,7 +42,12 @@ BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 BuildRequires:  asciidoc
 BuildRequires:  autoconf
 BuildRequires:  automake
+BuildRequires:  pkgconfig
+%if 0%{?suse_version}
 BuildRequires:  glib2-devel
+%else
+BuildRequires:  pkgconfig(glib-2.0)
+%endif
 BuildRequires:  libgcrypt-devel
 %if 0%{?fedora} || 0%{?centos} || 0%{?rhel}
 BuildRequires:  cluster-glue-libs-devel
@@ -52,7 +57,6 @@ BuildRequires:  libglue-devel
 BuildRequires:  libpacemaker-devel
 %endif
 BuildRequires:  libxml2-devel
-BuildRequires:  pkgconfig
 BuildRequires:  zlib-devel
 %if 0%{?fedora} || 0%{?centos} || 0%{?rhel}
 Requires:       pacemaker >= 1.1.8