[Docs] Bump minimum required version of GCC to 4.8

Author: fanquake

doc/dependencies.md

@@ -13,7 +13,7 @@ These are the dependencies currently used by Bitcoin Core. You can find instruct
 | Expat | [2.2.1](https://libexpat.github.io/) |  | No | Yes |  |
 | fontconfig | [2.12.1](https://www.freedesktop.org/software/fontconfig/release/) |  | No | Yes |  |
 | FreeType | [2.7.1](http://download.savannah.gnu.org/releases/freetype) |  | No |  |  |
-| GCC |  | [4.7+](https://gcc.gnu.org/) |  |  |  |
+| GCC |  | [4.8+](https://gcc.gnu.org/) |  |  |  |
 | HarfBuzz-NG |  |  |  |  |  |
 | libevent | [2.1.8-stable](https://github.com/libevent/libevent/releases) | 2.0.22 | No |  |  |
 | libjpeg |  |  |  |  | [Yes](https://github.com/bitcoin/bitcoin/blob/master/depends/packages/qt.mk#L75) |

doc/release-notes.md

@@ -56,6 +56,11 @@ frequently tested on them.
 Notable changes
 ===============
 
+GCC 4.8.x
+--------------
+The minimum version of GCC required to compile Bitcoin Core is now 4.8. No effort will be
+made to support older versions of GCC. See discussion in issue #11732 for more information.
+
 HD-wallets by default
 ---------------------
 Due to a backward-incompatible change in the wallet database, wallets created