Include stdio.h when checking for headers.
Include stdio.h when checking for headers.

The header readline/readline.h, and potentially millions of others, have an
implicit dependency on this header. Not including this header would result in a
header check failure.

digitalextremist/rubinius,Azizou/rubinius,ngpestelos/rubinius,kachick/rubinius,benlovell/rubinius,Wirachmat/rubinius,ngpestelos/rubinius,sferik/rubinius,sferik/rubinius,ruipserra/rubinius,mlarraz/rubinius,heftig/rubinius,jsyeo/rubinius,Azizou/rubinius,ruipserra/rubinius,Azizou/rubinius,dblock/rubinius,mlarraz/rubinius,ngpestelos/rubinius,jemc/rubinius,sferik/rubinius,ngpestelos/rubinius,mlarraz/rubinius,Wirachmat/rubinius,sferik/rubinius,jsyeo/rubinius,mlarraz/rubinius,jsyeo/rubinius,benlovell/rubinius,mlarraz/rubinius,mlarraz/rubinius,ruipserra/rubinius,digitalextremist/rubinius,digitalextremist/rubinius,benlovell/rubinius,kachick/rubinius,jemc/rubinius,mlarraz/rubinius,jsyeo/rubinius,ngpestelos/rubinius,dblock/rubinius,dblock/rubinius,jsyeo/rubinius,jemc/rubinius,kachick/rubinius,digitalextremist/rubinius,ruipserra/rubinius,kachick/rubinius,dblock/rubinius,Wirachmat/rubinius,heftig/rubinius,benlovell/rubinius,sferik/rubinius,digitalextremist/rubinius,jemc/rubinius,ruipserra/rubinius,dblock/rubinius,jsyeo/rubinius,digitalextremist/rubinius,heftig/rubinius,Azizou/rubinius,jemc/rubinius,Wirachmat/rubinius,benlovell/rubinius,benlovell/rubinius,kachick/rubinius,Azizou/rubinius,kachick/rubinius,Wirachmat/rubinius,kachick/rubinius,Wirachmat/rubinius,jemc/rubinius,sferik/rubinius,heftig/rubinius,heftig/rubinius,dblock/rubinius,ruipserra/rubinius,benlovell/rubinius,Azizou/rubinius,heftig/rubinius,kachick/rubinius,ruipserra/rubinius,jemc/rubinius,ngpestelos/rubinius,digitalextremist/rubinius,ngpestelos/rubinius,dblock/rubinius,Azizou/rubinius,sferik/rubinius,Wirachmat/rubinius,jsyeo/rubinius,heftig/rubinius