Use RbConfig::CONFIG instead of deprecated Config::CONFIG.

ChangeLog

+2016-04-24  Kubo Takehiro  <kubo@jiubao.org>
+	* docs/report-installation-issue.md: Use RbConfig::CONFIG instead of
+	   deprecated Config::CONFIG.
+
 2016-04-24  Kubo Takehiro  <kubo@jiubao.org>
 	* lib/oci8/oci8.rb: Add OCI8::in_cond and OCI8:InCondBindHelper.
 	* test/test_all.rb, test/test_bind_array.rb: Add test of OCI8::in_cond.

docs/report-installation-issue.md

@@ -20,14 +20,14 @@ If it is a new one, post the following information to [github][].
 
          file `which ruby`
          ruby --version
-         ruby -r rbconfig -e "p Config::CONFIG['host']"
-         ruby -r rbconfig -e "p Config::CONFIG['CC']"
-         ruby -r rbconfig -e "p Config::CONFIG['CFLAGS']"
-         ruby -r rbconfig -e "p Config::CONFIG['LDSHARED']"
-         ruby -r rbconfig -e "p Config::CONFIG['LDFLAGS']"
-         ruby -r rbconfig -e "p Config::CONFIG['DLDLAGS']"
-         ruby -r rbconfig -e "p Config::CONFIG['LIBS']"
-         ruby -r rbconfig -e "p Config::CONFIG['GNU_LD']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['host']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['CC']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['CFLAGS']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['LDSHARED']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['LDFLAGS']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['DLDLAGS']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['LIBS']"
+         ruby -r rbconfig -e "p RbConfig::CONFIG['GNU_LD']"
          
          # if you use gcc,
          gcc --print-prog-name=ld