Revert "Only use official Pandoc intra word syntax (#269)"

Fixes issue #285 (for now).

This reverts commit 376f95f.

Author: alerque

syntax/pandoc.vim

@@ -317,7 +317,7 @@ syn match pandocCiteLocator /[\[\]]/ contained containedin=pandocPCite,pandocICi
 " Text Styles: {{{2
 
 " Emphasis: {{{3
-call s:WithConceal("block", 'syn region pandocEmphasis matchgroup=pandocOperator start=/\\\@1<!\(\_^\|\s\|\S\|[[:punct:]]\)\@<=\*\S\@=/ skip=/\(\*\*\|__\)/ end=/\S\@1<=\*\(\s\|\S\|[[:punct:]]\)\@=/ contains=@Spell,pandocNoFormattedInEmphasis,pandocLatexInlineMath,pandocAmpersandEscape', 'concealends')
+call s:WithConceal("block", 'syn region pandocEmphasis matchgroup=pandocOperator start=/\\\@1<!\(\_^\|\s\|[[:punct:]]\)\@<=\*\S\@=/ skip=/\(\*\*\|__\)/ end=/\*\([[:punct:]]\|\s\|\_$\)\@=/ contains=@Spell,pandocNoFormattedInEmphasis,pandocLatexInlineMath,pandocAmpersandEscape', 'concealends')
 call s:WithConceal("block", 'syn region pandocEmphasis matchgroup=pandocOperator start=/\\\@1<!\(\_^\|\s\|[[:punct:]]\)\@<=_\S\@=/ skip=/\(\*\*\|__\)/ end=/\S\@1<=_\([[:punct:]]\|\s\|\_$\)\@=/ contains=@Spell,pandocNoFormattedInEmphasis,pandocLatexInlineMath,pandocAmpersandEscape', 'concealends')
 " }}}3