Delete vendored code and update CI to Go 1.13 (#158)

As the Go community transitions to using the modules ecosystem,
we want to only support one way of managing dependencies.
So this change moves to only using Go modules for dependency management.

This means that our effective minimum Go version increases to Go 1.11.
To account for this, we also update:
  - the documentation
  - Makefile
  - CI scripts

1 files changed, 0 insertions, 43 deletions

diff --git a/vendor/golang.org/x/sys/cpu/cpu_gccgo.c b/vendor/golang.org/x/sys/cpu/cpu_gccgo.c
deleted file mode 100644
index e363c7d..0000000
--- a/vendor/golang.org/x/sys/cpu/cpu_gccgo.c
+++ /dev/null
@@ -1,43 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-// +build 386 amd64 amd64p32
-// +build gccgo
-
-#include <cpuid.h>
-#include <stdint.h>
-
-// Need to wrap __get_cpuid_count because it's declared as static.
-int
-gccgoGetCpuidCount(uint32_t leaf, uint32_t subleaf,
-                   uint32_t *eax, uint32_t *ebx,
-                   uint32_t *ecx, uint32_t *edx)
-{
-	return __get_cpuid_count(leaf, subleaf, eax, ebx, ecx, edx);
-}
-
-// xgetbv reads the contents of an XCR (Extended Control Register)
-// specified in the ECX register into registers EDX:EAX.
-// Currently, the only supported value for XCR is 0.
-//
-// TODO: Replace with a better alternative:
-//
-//     #include <xsaveintrin.h>
-//
-//     #pragma GCC target("xsave")
-//
-//     void gccgoXgetbv(uint32_t *eax, uint32_t *edx) {
-//       unsigned long long x = _xgetbv(0);
-//       *eax = x & 0xffffffff;
-//       *edx = (x >> 32) & 0xffffffff;
-//     }
-//
-// Note that _xgetbv is defined starting with GCC 8.
-void
-gccgoXgetbv(uint32_t *eax, uint32_t *edx)
-{
-	__asm("  xorl %%ecx, %%ecx\n"
-	      "  xgetbv"
-	    : "=a"(*eax), "=d"(*edx));
-}