gnu: QEMU: Update to 5.0.0.

gnu: QEMU: Update to 5.0.0.

* gnu/packages/patches/qemu-CVE-2020-1711.patch,
gnu/packages/patches/qemu-CVE-2020-7039.patch,
gnu/packages/patches/qemu-CVE-2020-7211.patch,
gnu/packages/patches/qemu-CVE-2020-8608.patch,
gnu/packages/patches/qemu-fix-documentation-build-failure.patch: Delete files.
* gnu/local.mk (dist_patch_DATA): Adjust accordingly.
* gnu/packages/virtualization.scm (qemu)[source](patches): Remove.
[arguments]: Add phase 'patch-/bin/sh-references'.  In the 'configure' phase,
add shebang substitutions.  Remove phase 'prevent-network-configuration'.
[inputs]: Change from LIBCAP to LIBCAP-NG.