[epiphany] Use a bit more AX_REQUIRE_DEFINED

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 76a858119069e80c69bf19777a4c7334d6d55180
Author: Michael Catanzaro <mcatanzaro gnome org>
Date:   Thu Nov 10 17:32:56 2016 -0600

    Use a bit more AX_REQUIRE_DEFINED

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index c3ed2e3..d93027e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -23,6 +23,8 @@ AX_REQUIRE_DEFINED([AX_COMPILER_FLAGS])
 AX_REQUIRE_DEFINED([AX_GENERATE_CHANGELOG])
 AX_REQUIRE_DEFINED([AX_IS_RELEASE])
 AX_REQUIRE_DEFINED([GLIB_GSETTINGS])
+AX_REQUIRE_DEFINED([PKG_CHECK_EXISTS])
+AX_REQUIRE_DEFINED([PKG_CHECK_MODULES])
 AX_REQUIRE_DEFINED([YELP_HELP_INIT])
 
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