Improve printing of try block expressions

Previously, try blocks didn't quite show their catch statements correctly, and they completely failed to display nicely when a finally block was included:

    julia> :(try; do_try() catch end)
    :(try  # line 1:
            do_try()
        end)

    julia> :(try; do_try() catch do_catch() end)
    :(try  # line 1:
            do_try()
        catch false
            do_catch()
        end)

    julia> :(try; do_try() finally do_final() end)
    :($(Expr(:try, :(begin  # line 1:
            do_try()
        end), false, false, :(begin  # line 1:
            do_final()
        end))))

With this patch, they display correctly and look much more like the written syntax:

    julia> :(try; do_try() catch end)
    :(try  # line 1:
            do_try()
        catch
        end)

    julia> :(try; do_try() catch do_catch() end)
    :(try  # line 1:
            do_try()
        catch
            do_catch()
        end)

    julia> :(try; do_try() finally do_final() end)
    :(try  # line 1:
            do_try()
        finally  # line 1:
            do_final()
        end)
add list of mathematical symbols to allow as identifiers
Merge pull request #6857 from mbauman/better-try-expr-show

Improve printing of try block expressions
Fix type-stability issue in example life_rule.
Merge pull request #6858 from ArchRobison/adr/lifedoc

Fix type-stability issue in example life_rule.
In latest llvm SVN, the "useCFI" arguement was removed from createAsmStreamer()
enumerate(x) documentation update

Added example and added "plain english" explanation of when the function is useful
Merge pull request #6861 from JuliaLang/kms/llvm-3.5-update

In latest llvm SVN, the "useCFI" arguement was removed from createAsmStreamer()
fix #6808 and #6854

when tests are run on a single core, the RNG ends up with sprb45 having 16 nonzeros
Fix edit() when editor is Sublime with arguments

Example: EDITOR="sublime --wait"
Minor revisions on LinAlg docs 

Formated a few examples, added some returned values, etc
Merge pull request #6862 from brk00/patch-2

enumerate(x) documentation update
Merge pull request #6865 from jayschwa/fix-sublime-with-args

Fix edit() when editor is Sublime with arguments
Merge pull request #6867 from brk00/patch-4

Minor revisions on LinAlg docs
Merge pull request #6863 from tkelman/patch-4

fix #6808 and #6854
doc spelling: witch => which
Merge branch 'master' of github.com:JuliaLang/julia