Record source column positions

And:
- display them in stack traces
- expose them as Function.prototype.columnNumber

OP_line_num is renamed to OP_source_loc and the pc2line data structure
is extended with the column number in zigzag encoding.

The bytecode version number BC_VERSION is incremented because pc2line
data is read and written by JS_ReadObject() and JS_WriteObject() when
it is present.

Fixes: #149

Author: bnoordhuis

quickjs-atom.h

@@ -81,6 +81,7 @@ DEF(empty_string, "")
 DEF(length, "length")
 DEF(fileName, "fileName")
 DEF(lineNumber, "lineNumber")
+DEF(columnNumber, "columnNumber")
 DEF(message, "message")
 DEF(cause, "cause")
 DEF(errors, "errors")

quickjs-opcode.h

@@ -44,6 +44,7 @@ FMT(loc)
 FMT(arg)
 FMT(var_ref)
 FMT(u32)
+FMT(u32x2)
 FMT(i32)
 FMT(const)
 FMT(label)
@@ -281,7 +282,7 @@ def(scope_put_private_field, 7, 2, 0, atom_u16) /* obj value ->, emitted in phas
 
 def( set_class_name, 5, 1, 1, u32) /* emitted in phase 1, removed in phase 2 */
 
-def(       line_num, 5, 0, 0, u32) /* emitted in phase 1, removed in phase 3 */
+def(     source_loc, 9, 0, 0, u32x2) /* emitted in phase 1, removed in phase 3 */
 
 DEF(    push_minus1, 1, 0, 1, none_int)
 DEF(         push_0, 1, 0, 1, none_int)