Remove generated Inventor/system/inttypes header

[tritao]

This removes the generated include/Inventor/system/inttypes.h compatibility header and the associated configure/build plumbing.

Coin now exposes the standard fixed-width and size-related types from Inventor/C/basic.h via <stdint.h> and <stddef.h>, which already sits under SbBasic.h and the public C API headers. The few implementation-only cases that need more than that keep direct standard includes locally:

• <inttypes.h> for SCN* macros
• <sys/types.h> where off_t is used

Why

Inventor/system/inttypes.h is legacy compatibility machinery that we do not need anymore. We can just assume the standard headers exist and stop carrying a generated wrapper plus all the related configure/install logic.

This also keeps the public header cleanup centralized instead of spreading direct <stdint.h> includes across the API surface.

Included cleanup

This change also removes the obsolete integer-type detection/configuration pieces that only existed to support the generated header, including:

• the inttypes.h template files
• the related CMake and Automake install/build rules
• the old HAVE_* / COIN_* integer typedef plumbing in config templates
• stale comments and sanity checks that depended on that machinery

[Lgt2x]

bumped somewhere in FC?