[gnumeric] Compilation: missing prototypes are henceforth hard errors.

[Morten Welinder <mortenw src gnome org>]

commit e9818f0df3664e725f8665cd2f0912c6ff501aaf
Author: Morten Welinder <terra gnome org>
Date:   Fri Feb 15 18:55:21 2013 -0500

    Compilation: missing prototypes are henceforth hard errors.
    
    They lead to too many sneaky problems later, especially on 64-bit.

 configure.ac |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 852c3d7..c8e7ae7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -264,6 +264,8 @@ if test "$GCC" = yes -a "x$set_more_warnings" != xno; then
                         -Wchar-subscripts -Wwrite-strings \
                         -Wdeclaration-after-statement -Wnested-externs \
                         -Wmissing-noreturn -Wmissing-prototypes \
+                        -Werror=missing-prototypes -Werror=nested-externs \
+                        -Werror=implicit-function-declaration \
                         -Wmissing-declarations -Wno-pointer-sign \
                         -Werror=format-security -Wbitwise -Wcast-to-as \
                         -Wdefault-bitfield-sign -Wdo-while -Wparen-string \