Bump to 1.38.0

[revarbat]

Minor release: a new language feature.

• profile_time() (profile_time(): time a block's script and geometry, or an expression #236, parser profile_time(): reserved keyword, statement and expression forms openscad_cpp_parser#14): profile_time("label") { ... } prints the children's script and geometry time; x = profile_time("label") expr; prints the expression's time and yields its value. profile_time becomes a reserved keyword; supported_feature("profile-time") = 1.

Release checks

• BOSL2 docsgen A/B (1.37.1 vs main @ c51b76e, BOSL2 @ e173fa0a): 56 md identical, 2650 images with zero pixel changes, zero error/warning lines, logs identical.
• Binding tests 62/62 against a wheel built from main; C++ suite 2040/2040.

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