loader: report all type and syntax errors possible

Previously the loader would only report the first error. With this
change, all syntax and type errors will be reported.

testdata/errors/multi-1/types.go

@@ -0,0 +1,3 @@
+package typesmulti3
+
+var _ int = 3.14

testdata/errors/multi-2/syntax.go

@@ -0,0 +1,4 @@
+package syntaxmulti2
+
+func Foo2(type) {
+}

testdata/errors/multi-3/syntax.go

@@ -0,0 +1,4 @@
+package syntaxmulti1
+
+func Foo1(import) {
+}

testdata/errors/multi.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	_ "github.com/tinygo-org/tinygo/testdata/errors/multi-1"
+	_ "github.com/tinygo-org/tinygo/testdata/errors/multi-2"
+	_ "github.com/tinygo-org/tinygo/testdata/errors/multi-3"
+)
+
+func main() {
+}
+
+// ERROR: # github.com/tinygo-org/tinygo/testdata/errors/multi-2
+// ERROR: multi-2/syntax.go:3:11: expected ')', found 'type'
+// ERROR: # github.com/tinygo-org/tinygo/testdata/errors/multi-3
+// ERROR: multi-3/syntax.go:3:11: expected ')', found 'import'
+// ERROR: # github.com/tinygo-org/tinygo/testdata/errors/multi-1
+// ERROR: multi-1/types.go:3:13: cannot use 3.14 (untyped float constant) as int value in variable declaration (truncated)