Make Basis look column-major while retaining a row-major representation

Per https://github.com/godotengine/godot/issues/14553:
Godot stores Basis in row-major layout for more change for efficiently
taking advantage of SIMD instructions, but in scripts Basis looks like and
is accessible in a column-major format.

This change modifies the C++ binding so that from the script's perspective
Basis does look like if it was column-major while retaining a row-major
in-memory representation. This is achieved using a set of helper template
classes which allow accessing individual columns whose components are
non-continues in memory as if it was a Vector3 type. This ensures script
interface compatibility without needing to transpose the Basis every time
it is passed over the script-engine boundary.

Also made most of the Vector2 and Vector3 class interfaces inlined in the
process for increased performance.

While unrelated (but didn't want to file a separate PR for it), this change
adds the necessary flags to have debug symbol information under MSVC.

Fixes #241.

src/core/Basis.cpp

@@ -31,15 +31,6 @@ Basis::Basis() {
 	elements[2][2] = 1;
 }
 
-const Vector3 &Basis::operator[](int axis) const {
-
-	return elements[axis];
-}
-Vector3 &Basis::operator[](int axis) {
-
-	return elements[axis];
-}
-
 #define cofac(row1, col1, row2, col2) \
 	(elements[row1][col1] * elements[row2][col2] - elements[row1][col2] * elements[row2][col1])