Oracle PLSQL lexer (suitable for Oracle SQL as well) (#1811)

* add oracle plsql lexer

* add demo and sample

* tweak rules for multiline items and function/package/procedure/type creates

* add type attributes, word operators, preprocessor directives

* add rule for MERGE syntax to get keywords rather than names

* remove trailing dot option for floating point number.
restrict words after dot to functions or regular names instead of keywords

* pad visual sample with more edge cases on numbers and dot method notation.
Add comments to lexer code and pretty it up

* added PLSQL to docs/Languages.md
ensure 2 space indentation throughout
correct spelling errors in comments
change keywords to keywords_reserved and keywords_nresvd to keywords
Remove redundant comments
add cursor attributes to name::attribute list
add optional double/float modifier letters to numeric literals, also to visual test file.

* slight formatting tweak. remove extra space

docs/Languages.md

@@ -144,6 +144,7 @@
 - PHP (`php`)
 - Plain Text (`plaintext`)
 - Plist (`plist`)
+- PLSQL (`plsql`)
 - Pony (`pony`)
 - PostScript (`postscript`)
 - powershell (`powershell`)

lib/rouge/demos/plsql

@@ -0,0 +1,2 @@
+SELECT q'{a quoted string}' AS s, TO_CHAR(SYSDATE,'MM/DD/YYYY') AS "Current Date" FROM DUAL
+WHERE 1=1;