Linux: Added CMake script for creating .DEBs and .RPMs for VeraCrypt using CPack, and shell scripts which build then package VeraCrypt under CentOS and Debian/Ubuntu. (#511)

The DEB script builds VeraCrypt and links it against wxWidgets that comes with the distribution.
The RPM script awaits for wxWidgets-3.0.4 source code which it builds then links VeraCrypt statically to it.
Both scripts create the corresponding package after the build.

src/Build/Packaging/debian-control/prerm

@@ -0,0 +1,9 @@
+#!/bin/sh
+V="$(mount | grep veracrypt_aux_mnt)"
+if [ ! -z "$V" ]
+then
+	echo "Error: All VeraCrypt volumes must be dismounted first." 
+	exit 1
+else
+	exit 0
+fi 

src/Build/Packaging/rpm-control/prerm.sh

@@ -0,0 +1,9 @@
+#!/bin/sh
+V="$(mount | grep veracrypt_aux_mnt)"
+if [ ! -z "$V" ]
+then
+	echo "Error: All VeraCrypt volumes must be dismounted first." 
+	exit 1
+else
+	exit 0
+fi