[Reportbug-maint] Bug#363920: New patch to check mua

[chaica]

tags 363920 patch
thanks

Hi,

Here is a better patch for this bug : 
* checks if the mua is supported by reportbug
* checks if the mua is executable on the system
* if --mua option is defined with --mua 'mua', it replaces the mua name
with mua name + the good options to use it with reportbug

NB : if someone uses --mua 'mua --groovy-options --another-one', he's on
his own, we can not check every combinations of every options of the
supported commands. But the checks described above apply in every
situations.

Bye,
Carl Chenet