C lexer doesn't completely highlight some floating point literals

[Anteru]

(Original issue 1292 created by None on 2016-10-13T00:04:14.400878+00:00)

Two types of floating point literals are not handled correctly.

Decimal floating point literals with an exponent part:
In "12.45e78f" the 'f' is not highlighted, while in "12.45e78u" the 'u' is incorrectly accepted.

Hexadecimal floating point literals:
In "0x12.34p56f" nothing after the '.' is highlighted.

[Anteru]

Fixed by #1350