compiler: make compiler an ordinary vlib/compiler module

* Move compiler/ under vlib/compiler/ .

* Add a minimal compiler/main.v driver program.

* Cleanup compiler/main.v .

* Make most compiler tests pass again.

* Apply the fix by @joe-conigliaro , so that the rest of the compiler tests are fixed too.

* Thanks to @avitkauskas, now the vlib/vcompiler/tests/str_gen_test.v test does not need to be special cased anymore.

* Reapply @joe-conigliaro fix for vgen.

vlib/compiler/tests/msvc_test.v

@@ -0,0 +1,49 @@
+fn test_flag_parsing() {
+	mut rest := '-lGlfw -f gl2,-ltest_nice_meme,-l cc,-Ldl test.o a.o ' //, whatever.o'
+	result := ['-l', 'Glfw', 
+			   '-f', 'gl2', 
+			   '-l', 'test_nice_meme', 
+			   '-l', 'cc',
+			   '-L', 'dl',
+			   '', 'test.o',
+			   '', 'a.o']
+
+	mut flags := []string
+	for {
+		mut base := rest
+
+		fl := if rest.starts_with('-') {
+			base = rest.right(2).trim_space()
+			rest.left(2)
+		} else {
+			''
+		}
+
+		// Which ever one of these is lowest we use
+		// TODO: we really shouldnt support all of these cmon
+		mut lowest := base.index('-')
+		for x in [base.index(' '), base.index(',')] {
+			if (x < lowest && x != -1) || lowest == -1 {
+				lowest = x
+			}
+		}
+		arg := if lowest != -1 {
+			rest = base.right(lowest).trim_space().trim(',')
+			base.left(lowest).trim_space().trim(',')
+		} else {
+			rest = ''
+			base.trim_space()
+		}
+
+		flags << fl
+		flags << arg
+
+		if rest.len == 0 {
+			break
+		}
+	}
+
+	for i, f in flags {
+		assert f == result[i] 
+	}
+}