[librsvg] Bump minimum Rust version to 1.34

[Federico Mena Quintero <federico src gnome org>]

commit f304e8440737dd77531afb15ffbf4eb906ef5d68
Author: Federico Mena Quintero <federico gnome org>
Date:   Thu Jul 11 18:24:51 2019 -0500

    Bump minimum Rust version to 1.34
    
    The last merge to update gtk-rs needs TryFrom, which got stabilized in
    Rust 1.34.

 COMPILING.md | 2 +-
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/COMPILING.md b/COMPILING.md
index ef6f5eb7..d2054efd 100644
--- a/COMPILING.md
+++ b/COMPILING.md
@@ -32,7 +32,7 @@ minimum version is listed here; you may use a newer version instead.
 **Compilers:**
 
 * a C compiler and `make` tool; we recommend GNU `make`.
-* rust 1.31 or later
+* rust 1.34 or later
 * cargo
 
 **Mandatory dependencies:**
diff --git a/configure.ac b/configure.ac
index b9f7e4b3..e416231a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -113,7 +113,7 @@ AC_CHECK_PROGS(AR, ar)
 dnl Minimum version of rustc that we support
 dnl If you change this, please update COMPILING.md
 MINIMUM_RUST_MAJOR=1
-MINIMUM_RUST_MINOR=31
+MINIMUM_RUST_MINOR=34
 
 rust_version=`$RUSTC --version`
 version=`echo "$rust_version" | sed -e 's/^rustc //g'`