Getting a lot of warnings from the compiler

[isaacvr]

Describe the bug
There are a lot of warnings from the compiler

Environment information:

• Platform: Linux 4.19.0-1-amd64 Migrate repository from skycoin/skycoin #1 SMP Debian 4.19.12-1 (2018-12-22) x86_64
• Go environment: go version go1.11.6 linux/amd64

GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myuser/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/usr/share/gocode"
GOPROXY=""
GORACE=""
GOROOT="/usr/lib/go"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build305345991=/tmp/go-build -gno-record-gcc-switches"

• Compiler info: gcc (Debian 8.3.0-6) 8.3.0

Steps to Reproduce
Steps to reproduce the behavior:

1. Go to the source project root dir
2. Run make test-libc

Actual behavior

Getting a lot of warnings:

lib/cgo/tests/check_cipher.crypto.c: In function ‘TestSecKeyFromHex’:
lib/cgo/tests/check_cipher.crypto.c:269:27: warning: passing argument 2 of ‘SKY_cipher_RandByte’ from incompatible pointer type [-Wincompatible-pointer-types]
   SKY_cipher_RandByte(32, &b);
                           ^~
In file included from lib/cgo/tests/check_cipher.crypto.c:5:
cgo-gcc-export-header-prolog:330:62: note: expected ‘coin__UxArray *’ {aka ‘struct <anonymous> *’} but argument is of type ‘GoSlice *’ {aka ‘struct <anonymous> *’}
In file included from lib/cgo/tests/check_cipher.hash.c:4:
lib/cgo/tests/check_cipher.hash.c: In function ‘TestSHA256Hex’:
lib/cgo/tests/check_cipher.hash.c:137:15: warning: implicit declaration of function ‘isGoStringEq’; did you mean ‘isGoSliceEq’? [-Wimplicit-function-declaration]
     ck_assert(isGoStringEq(s, s2));
               ^~~~~~~~~~~~
lib/cgo/tests/check_params.distribution.c: In function ‘TestDistributionAddressArrays’:
lib/cgo/tests/check_params.distribution.c:33:22: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
     for (i = 0, iStr = (GoString_ *)all.data; i < all.len; ++i, ++iStr)
                      ^
lib/cgo/tests/check_params.distribution.c:42:22: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
     for (i = 0, iStr = (GoString_ *)unlocked.data; i < unlocked.len; ++i, ++iStr)
                      ^
lib/cgo/tests/check_params.distribution.c:51:40: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
         for (k = 0, notfound = 1, kStr = (GoString_ *)all.data; notfound && (k < all.len); ++k, ++kStr)
                                        ^
lib/cgo/tests/check_params.distribution.c:58:22: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
     for (i = 0, iStr = (GoString_ *)locked.data; i < locked.len; ++i, ++iStr)
                      ^
lib/cgo/tests/check_params.distribution.c:67:40: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
         for (k = 0, notfound = 1, kStr = (GoString_ *)all.data; notfound && k < all.len; ++k, ++kStr)
                                        ^
lib/cgo/tests/check_params.distribution.c:75:40: warning: assignment to ‘GoString *’ {aka ‘struct <anonymous> *’} from incompatible pointer type ‘GoString_ *’ {aka ‘struct <anonymous> *’} [-Wincompatible-pointer-types]
         for (k = 0, notfound = 1, kStr = (GoString_ *)unlocked.data; notfound && k < unlocked.len; ++k, ++kStr)
.
.
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Expected behavior
No warning at all