* Split get_compiler_version into two functions:
get_compiler_version_output runs the compiler with the relevant
option to print the version; extract_version_from_output determines
the version by examining this output. This makes it easier to test
the customized version detection for each compiler. Users can
customize this by overriding the following:
* version_argument: this is the argument that tells the compiler to
print its version. It assumes that the compiler will report its
version if invoked with a single option (like "--version")
* version_regex: the regular expression used to extract the version
from the compiler argument. This assumes that a regular
expression is sufficient to extract the version, and that the
version can be extracted from a single capture group (Spack uses
the first capture group)
* default_version: allows you to completely override all version
detection logic
* get_compiler_version_output: if getting the compiler to report
its version is more complex than invoking it with a single arg
* extract_version_from_output: if it is difficult to define a regex
that can be used to extract the version from the output
* Added tests for version detection of most compilers
* Removed redundant code from xl_r compiler class (by inheriting
from xl compiler definition)
a1255b61c0