[Lexer] Add test case for erroneous hex number literal

[rintaro]

What's in this pull request?

Follow up on #3124 and #3132 .

CC: @jckarter

var fl_t: Float = 0x1.p // expected-error {{value of type 'Int' has no member 'p'}}
var fl_u: Float = 0x1.p2 // expected-error {{value of type 'Int' has no member 'p2'}}
var fl_v: Float = 0x1.p+ // expected-error {{'+' is not a postfix unary operator}}
var fl_w: Float = 0x1.p+2 // expected-error {{value of type 'Int' has no member 'p'}}

Added in float literal test cases. Is it OK?

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Before merging this pull request to apple/swift repository:

• Test pull request on Swift continuous integration.

[lattner]

Nice.

@swift-ci please test and merge

[jckarter]

LGTM, thanks @rintaro !

[rintaro]

https://ci.swift.org/job/swift-PR-merge/506/
All tests are passed, but CI failed to merge. I'm going to merge this manually.

[lattner]

Thanks!