Fix build warnings produced by rustc 1.41.1

[mikemadden42]

These changes fix the following warnings:

warning: `...` range patterns are deprecated
  --> src/arch/x86/prefixx86.rs:76:13
--
warning: `...` range patterns are deprecated
   --> src/arch/x86/prefixx86.rs:198:13
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21496:24
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21497:24
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21498:24
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21499:24
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21653:18
--
warning: `...` range patterns are deprecated
     --> src/arch/x86/displayx86.rs:21703:34
--
warning: use of deprecated item 'core::str::<impl str>::trim_right_matches': superseded by `trim_end_matches`
   --> src/analysis/signature_analysis.rs:226:31
--
warning: use of deprecated item 'core::str::<impl str>::trim_left_matches': superseded by `trim_start_matches`
   --> src/analysis/signature_analysis.rs:254:74
--
warning: use of deprecated item 'core::str::<impl str>::trim_right_matches': superseded by `trim_end_matches`
   --> src/analysis/signature_analysis.rs:254:97
--
warning: use of deprecated item 'core::str::<impl str>::trim_left_matches': superseded by `trim_start_matches`
   --> src/analysis/signature_analysis.rs:265:79
--
warning: use of deprecated item 'core::str::<impl str>::trim_left_matches': superseded by `trim_start_matches`
   --> src/analysis/signature_analysis.rs:265:102
--
warning: use of deprecated item 'core::str::<impl str>::trim_right_matches': superseded by `trim_end_matches`
   --> src/analysis/signature_analysis.rs:265:125
--
warning: use of deprecated item 'core::str::<impl str>::trim_right_matches': superseded by `trim_end_matches`
   --> src/analysis/signature_analysis.rs:388:31
--
warning: variable does not need to be mutable
   --> src/arch/x86/emulatex86.rs:736:18
--
warning: variable does not need to be mutable
   --> src/arch/x86/emulatex86.rs:764:18
--
warning: variable does not need to be mutable
   --> src/arch/x86/emulatex86.rs:793:18
--
warning: variable does not need to be mutable
    --> src/arch/x86/emulatex86.rs:1635:17
--
warning: variable does not need to be mutable
    --> src/arch/x86/emulatex86.rs:2001:29
--
warning: variable does not need to be mutable
    --> src/arch/x86/emulatex86.rs:2012:29
--
warning: variable does not need to be mutable
    --> src/arch/x86/emulatex86.rs:2189:29
--
warning: variable does not need to be mutable
    --> src/arch/x86/emulatex86.rs:2200:29
--
warning: variable does not need to be mutable
   --> src/analysis/data_analyzer.rs:172:21
--
warning: variable does not need to be mutable
   --> src/analysis/signature_analysis.rs:264:37
--
warning: variable does not need to be mutable
   --> src/analysis/signature_analysis.rs:332:33

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[rseymour]

does what it says on the tin.