gcc: Identifiers implementation

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1 4.3 Identifiers
1 ===============
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1    * 'Which additional multibyte characters may appear in identifiers
1      and their correspondence to universal character names (C99 and C11
1      6.4.2).'
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11      ⇒Implementation-defined behavior (cpp)Implementation-defined
      behavior.
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1    * 'The number of significant initial characters in an identifier (C90
1      6.1.2, C90, C99 and C11 5.2.4.1, C99 and C11 6.4.2).'
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1      For internal names, all characters are significant.  For external
1      names, the number of significant characters are defined by the
1      linker; for almost all targets, all characters are significant.
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1    * 'Whether case distinctions are significant in an identifier with
1      external linkage (C90 6.1.2).'
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1      This is a property of the linker.  C99 and C11 require that case
1      distinctions are always significant in identifiers with external
1      linkage and systems without this property are not supported by GCC.
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